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1

A Fast Method of Feature Extraction for Lowering Vehicle Pass-By Noise Based on Nonnegative Tucker3 Decomposition

Wang H., Cheng G., Deng G., Li X., Li H., Huang Y.

Archives of Acoustics

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2017

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Vol. 42, No. 4

619--629

EN

Usually, the judgement of one type fault of vehicle pass-by noise is difficult for engineers, especially when some significant features are disturbed by other interference noise, such as the squealing noise is almost simultaneous with the whistle in the exhaust system. In order to cope with this problem, a new method, with the antinoise ability of the algorithm on the condition by which the features are entangled, is developed to extract clear features for the fault analysis. In the proposed method, the nonnegative Tucker3 decomposition (NTD) with fast updating algorithm, signed as NTD_FUP, can find out the natural frequency of the parts/components from the exhaust system. Not only does the NTD_FUP extract clear features from the confused noise, but also it is superior to the traditional methods in practice. Then, an aluminium-foil alloy material, which is used for the heat shield for its lower noise radiation, replaces the aluminium alloy alone. Extensive experiments show that the sound pressure level of the vehicle pass-by noise is reduced 0.9 dB(A) by the improved heat shield, which is also considered as a more lightweight design for the exhaust system of an automobile.

2

Research on bispectrum analysis of secondary feature for vehicle exterior noise based on nonnegative tucker3 decomposition

Wang H., Deng G., Li Q., Kang Q.

Eksploatacja i Niezawodność

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2016

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Vol. 18, no. 2

291--298

EN

Nowadays, analysis of external vehicle noise has become more and more difficult for NVH (noise vibration and harshness) engineer to find out the fault among the exhaust system when some significant features are masked by the jamming signals, especially in the case of the vibration noise associating to the bodywork. New method is necessary to be explored and applied to decompose a high-order tensor and extract the useful features (also known as secondary features in this paper). Nonnegative Tucker3 decomposition (NTD) is proposed and applied into secondary feature extraction for its high efficiency of decomposition and well property of physical architecture, which serves as fault diagnosis of exhaust system for an automobile car. Furthermore, updating algorithm conjugating with Newton-Gaussian gradient decent is utilized to solve the problem of overfitting, which occurs abnormally on traditional iterative method of NTD. Extensive experimen results show the bispectrum of secondary features can not only exceedingly interpret the state of vehicle exterior noise, but also be benefit to observe the abnormal frequency of some important features masked before. Meanwhile, the overwhelming performance of NTD algorithm is verified more effective under the same condition, comparing with other traditional methods both at the deviation of successive relative error and the computation time.

PL

Obecnie inżynierowie NVH (zajmujący się problematyką hałasu, drgań i uciążliwości akustycznych) napotykają na coraz większe trudności przy analizie hałasu zewnętrznego pojazdów wynikające z faktu, że istotne cechy związane z nieprawidłowościami układu wydechowego są maskowane przez sygnały zakłócające, szczególnie hałas wibracyjny związany z pracą nadwozia. Niezbędna jest zatem nowa metoda, która pozwoli rozkładać tensory wysokiego rzędu i wyodrębniać przydatne cechy (zwane w tym artykule także cechami drugorzędnymi). Do ekstrakcji cech drugorzędnych wykorzystano w prezentowanej pracy metodę nieujemnej faktoryzacji tensorów znaną także jako nieujemna dekompozycja Tuckera 3 (NTD) , która cechuje się wysoką efektywnością dekompozycji i może być wykorzystywana w diagnostyce uszkodzeń układu wydechowego samochodów. Problem nadmiernego dopasowania, który występuje w tradycyjnej metodzie iteracyjnej NTD rozwiązano przy pomocy algorytmu aktualizacyjnego sprzężonego z gradientem prostym Newtona-Gaussa. Wyniki doświadczeń pokazują, że bispektrum cech drugorzędnych nie tylko pozwala doskonale interpretować stan hałasu zewnętrznego pojazdu, ale również umożliwia wykrywanie wcześniej maskowanych nieprawidłowych częstotliwości odpowiadających niektórym ważnym cechom. Badania potwierdzają, że algorytmu NTD jest bardziej efektywny, w tych samych warunkach, w porównaniu z innymi tradycyjnymi metodami zarówno w zakresie odchyleń błędu względnego jak i czasu obliczeń.

3

Insensitive HMX (Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) Nanocrystals Fabricated by High-Yield, Low-Cost Mechanical Milling

Wang Y., Jiang W., Song X., Deng G., Li F.

Central European Journal of Energetic Materials

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2013

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Vol. 10, no. 2

277--287

EN

A mechanical approach had been adopted for fabricating HMX nanoparticles. This fabrication method avoided the recrystallization process and was different from the traditional methods employed to prepare nanoexplosives. In particular, the high yield and low cost increased the possibility of its industrial application. Specifcally, HMX particles, that had a mean size of 0.27 μm, were prepared by mechanical milling; a signifcant proportion of nano-HMX (<100 nm) were present and these were observed by TEM and SEM images. The thermal decomposition of HMX samples before and after pulverization was investigated by TG/DSC analysis. The results indicated that there was no obvious difference between the thermographs of raw and pulverized HMX. The HMX samples were investigated by friction, impact, and shock sensitivity tests. High safety was confrmed since pulverized HMX was far more insensitive than raw HMX; indeed the shock sensitivity of pulverized HMX was about 60 percent lower than that of raw HMX.

4

Hybrid technique based on chirp effect and phase shifts for spectral Talbot effect in sampled fiber Bragg gratings (FBGs)

Deng G., Pan W.

Optica Applicata

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2011

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Vol. 41, nr 1

225--233

EN

To implement the spectral Talbot effect in sampled fiber Bragg gratings (SFBGs), a hybrid technique based on a chirp effect and phase shifts is proposed. Firstly, the general phase condition is derived as the principle of this hybrid technique, and it also can be used to demonstrate other reported techniques, including the linear chirp, the periodical chirp, and the multiple phase shift technique. According to the general phase condition and the equivalent chirp coefficient in the Talbot effect, multi-channel dispersion compensators are designed with different arrangements of chirp coefficient and phase shifts. Moreover, the dispersion value can be tuned in these devices by dynamically adjusting the phase shifts of the hybrid technique. Numerical simulations are carried out to confirm the performance of such devices realized by using the hybrid technique.