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Dayou, Jedol,Wang, Semyung Marcel Dekker inc. 2006 MECHANICS BASED DESIGN OF STRUCTURES AND MACHINES Vol.34 No.1
<P> The fixed-points theory has been used as one of the design laws in fabricating a vibration neutralizer for the control of a relatively simple structure. The underlying principle of the theory is that in the frequency response function (FRF) of the system considered, there exist two fixed points that are common to all FRF curves regardless of the damping value of the neutralizer. It is possible, with the proper selection of the neutralizer's resonance frequency, to determine the optimal damping value of the neutralizer that provides a smooth FRF by following the standard procedure of the theory. Recently, the authors have extended the application of the theory for global vibration control of a continuous structure with well separated natural frequencies. In this paper, the application is further extended to global vibration control of a structure with natural frequencies that are closely spaced. Through some numerical simulations, it is shown that the theory can also be used to remove the effects of the dominant mode within the frequency range where the global response is dominated by that mode. However, there are some limitations in its application especially for the overlapping natural frequencies.</P>
Increasing the Output from Piezoelectric Energy Harvester Using Width-Split Method with Verification
Chow Man Sang,Jedol Dayou,Willey Y. H. Liew 한국정밀공학회 2013 International Journal of Precision Engineering and Vol. No.
This paper proposes a new scheme for piezoelectric energy harvesting maximization. The proposed enhancement relies on a new topology of splitting a specified dimension piezo composite bender into beams with smaller width and, therefore, higher quality factor (or Q factor). The increase of Q factor allows a much more effective energy conversion process. It is shown that the proposed method,based on single splitting, increases the harvested power by a factor of up to √6, and up to √7.62 for two even-splitting compared to with no splitting. The wideband operation is accomplished by using different resonating benders in such a way that individual benders are each tuned to a different resonance frequency. Taking the configuration of single even-splitting as an example, the power output of the prototype was 39 μW at 27.2 Hz with 8 Hz bandwidth under 2 mm peak-to-peak input displacement and 3 Hz variation in resonant frequency. This corresponds to more than 2 times of power output with no splitting as well as about 23% increase in bandwidth. Such power output is sufficient to power up electronics devices such as a “2 AA dry cells-powered” digital clock with the wider range operating frequency.
Rouhollah Hosseini,Mohsen Hamedi,임종범,김재환,Jedol Dayou 한국정밀공학회 2017 International Journal of Precision Engineering and Vol.18 No.3
Electrical energy is normally generated through different sources such as hydroelectric, wind, heat, nuclear transformation, chemical reactions or vibrations. Nowadays, harvesting power from mechanical vibration is one of the novel technologies that usually can be done by systems based on electromagnetic, electrostatic, piezoelectric and combination of them. Piezoelectric systems can convert motion from the vibrating structures into electrical power. Cellulose Electro-active paper (EAPap) has been recognized as a novel smart piezoelectric material that can be used for energy harvesting purposes. One of the most prevalent method for vibration energy harvesting is using unimorph piezoelectric cantilever beams. In this paper, an analytical solution based on distributed parameter model is presented to calculate the generated energy from vibration of cantilever substrate that is partially covered by EAPap material. In the studied structure, piezoelectric layer thickness in comparison to the length of the beam and thickness of substrate material can be considered very thin. Thus its effect on the vibration behavior of structure is negligible. The results are validated by experimental values. The analytical data was found to be very close to experimental results and finite element simulation values. Findings from this study provide guidelines on system parameters that can be manipulated for more efficient performance in different ambient source conditions.
Muhammad Izzuddin Rumaling,Fuei Pien Chee,Jedol Dayou,Jackson Hian Wui Chang,Steven Soon Kai Kong,Justin SENTIAN 한국대기환경학회 2020 Asian Journal of Atmospheric Environment (AJAE) Vol.14 No.1
Missing data in large data analysis has affected further analysis conducted on dataset. To fill in missing data, Nearest Neighbour Method (NNM) and Expectation Maximization (EM) algorithm are the two most widely used methods. Thus, this research aims to compare both methods by imputing missing data of air quality in five monitoring stations (CA0030, CA0039, CA0042, CA0049, CA0050) in Sabah, Malaysia. PM10 (particulate matter with aerodynamic size below 10 microns) dataset in the range from 2003-2007 (Part A) and 2008-2012 (Part B) are used in this research. To make performance evaluation possible, missing data is introduced in the datasets at 5 different levels (5%, 10%, 15%, 25% and 40%). The missing data is imputed by using both NNM and EM algorithm. The performance of both data imputation methods is evaluated using performance indicators (RMSE, MAE, IOA, COD) and regression analysis. Based on performance indicators and regression analysis, NNM performs better compared to EM in imputing data for stations CA0039, CA0042 and CA0049. This may be due to air quality data missing at random (MAR). However, this is not the case for CA0050 and part B of CA0030. This may be due to fluctuation that could not be detected by NNM. Accuracy evaluation using Mean Absolute Percentage Error (MAPE) shows that NNM is more accurate imputation method for most of the cases.
HHT와 연속스캐닝 진동계를 이용한 구조물의 모드 형상 복원
경용수(Yongsoo Kyong),김대성(Daesung Kim),Jedol Dayou,박기환(Kyihwan Park),왕세명(Semyung Wang) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.6
For CSLDV, the Chebyshev demodulation (or polynomial) technique and Hilbert transform approach have been used for mode shape reconstruction with harmonic excitation. In this paper, the Hilbert-Huang transform approach was applied as an alternative to impact excitation cases in terms of a numerical approach. The vibration of the tested structure is modeled using impulse response functions. In order to verify this technique, a simply supported beam was chosen as the test rig. With additional innovative steps which are the ideal-band pass filter and the nodal point determination, Hilbert-Huang transformation can be used for a good mode shape reconstruction even in the impact excitation case.