Time–frequency interpretation of multi-frequency signal from rotating machinery using an improved Hilbert–Huang transform

The Hilbert–Huang transform (HHT) has proven to be a promising tool for the analysis of non-stationary signals commonly occurred in industrial machines. However, in practice, multi-frequency intrinsic mode functions (IMFs) and pseudo IMFs are likely generated and lead to grossly erroneous or even completely meaningless instantaneous frequencies, which raise difficulties in interpreting signal features by the HHT spectrum. To enhance the time–frequency resolution of the traditional HHT, an improved HHT is proposed in this study. By constructing a bank of partially overlapping bandpass filters, a series of filtered signals are obtained at first. Then a subset of filtered signals, each associated with certain energy-dominated components, are selected based on the maximal-spectral kurtosis–minimal-redundancy criterion and the information-related coefficient, and further decomposed by empirical mode decomposition to extract sets of IMFs. Furthermore, IMF selection scheme is applied to select the relevant IMFs on which the HHT spectrum is constructed. The novelty of this method is that the HHT spectrum is just constructed with the relevant, almost monochromatic IMFs rather than with the IMFs possibly with multiple frequency components or with pseudo components. The results on the simulated data, test rig data, and industrial gearbox data show that the proposed method is superior to the traditional HHT in feature extraction and can produce a more accurate time–frequency distribution for the inspected signal.     

Extraction of microseismic waveforms characteristics prior to rock burst using Hilbert–Huang transform

This study provides a new research idea concerning rock burst prediction. The characteristics of microseismic (MS) waveforms prior to and during the rock burst were studied through the Hilbert–Huang transform (HHT). In order to demonstrate the advantage of the MS features extraction based on HHT, the conventional analysis method (Fourier transform) was also used to make a comparison. The results show that HHT is simple and reliable, and could extract in-depth information about the characteristics of MS waveforms. About 10 days prior to the rock burst, the main frequency of MS waveforms transforms from the high-frequency to low-frequency. What’s more, the waveforms energy also presents accumulation characteristic. Based on our study results, it can be concluded that the MS signals analysis through HHT could provide valuable information about the coal or rock deformation and fracture.     

The morphological undecimated wavelet decomposition – Discrete cosine transform composite spectrum fusion algorithm and its application on hydraulic pumps

Degradation feature extraction of hydraulic pumps is a key step of the condition-based maintenance. In this paper, a novel method based on MUWD-DCS fusion algorithm is proposed. In order to decrease noises and disturbances, the method for obtaining detail components by the Morphological Undecimated Wavelet Decomposition (MUWD) with the selected parameters is presented firstly. Multi-channel vibration signals are proposed by the MUWD and the detail components containing sensitive information are achieved. Furthermore, on the basement of the earlier Composite Spectrum (CS), the DCS fusion algorithm is proposed to make fusion of the obtained detail components for improving the feature performance. The DCS entropy is extracted to be the degradation feature. Analysis of application on the hydraulic pump degradation experiment demonstrates that the proposed algorithm is feasible and it is effective to reveal the performance degradation of the hydraulic pump.     

Analysis of signal characteristics of swirlmeter in oscillatory flow based on Hilbert–Huang Transform (HHT)

In the paper, firstly, on an experimental facility, we investigated the measurement characteristics of a diameter 50 mm swirlmeter in uniform flow and oscillatory flow. At the same time, the interference characteristics of oscillatory flow were studied. Then, the signal characteristics of swirlmeter in oscillatory flow were analyzed by Hilbert–Huang Transform (HHT) method. Results show that the response characteristics of swirlmeter in oscillatory flow are addition of that of swirlmeter in uniform flow and the interference characteristics of oscillatory flow. They further prove the conclusions which suppose that the correlation between the velocity pressures of fluid disturbs wave and that of vortex precession in swirlmeter is linear in the literature, and a new method for the oscillatory flow swirlmeter noise removal on HHT was provided.     

Application of Hilbert–Huang Transform to acoustic emission signal for burn feature extraction in surface grinding process

This paper presents a sensor system using motor current sensors, voltage sensors, accelerator and acoustic emission sensor for grinding burn feature extraction. The new method, Hilbert–Huang transform (HHT), was applied as a signal processing tool to digest the raw acoustic emission and accelerator signals and to extract grinding burn features. A filtering criterion using average energy percentage of IMF components was proposed in order to simplify the calculation. Five IMF components were selected based on this criterion and their marginal spectra were calculated. The marginal spectral amplitude of the first three IMF components and the spectral centroid of the last two IMF components clearly reflected the occurrence of grinding burn. Results indicate that the application of HHT to acoustic emission signals in grinding burn detection is of great potential. Besides, the wheel rotation speed can be successfully uncovered through the intrinsic mode function (IMF), which verified the physical meaning of the EMD method.     

A new MNF–BM4D denoising algorithm based on guided filtering for hyperspectral images

This paper proposed a new MNF–BM4D denoising algorithm based on guided filtering to improve the denoising performance of the state-of-the-art Block-Matching and 4D filtering(BM4D) algorithm for hyperspectral images in the spatial and spectral domain. BM4D is firstly used to denoise hyperspectral images. Then Minimum Noise Fraction(MNF) algorithm is introduced to distinguish between the main component and the noisy component. Finally, the guided image filtering technology is utilized to further improve the denoising performance. A number of experiments on both simulated and real data are conducted to validate the effective denoising performance of the proposed method. Therefore, the proposed algorithm can be considered as a promising technique for hyperspectral imagery denoising.     

A signal interpolation method for Fabry–Perot interferometer utilized in mechanical vibration measurement

In this investigation, a self-developed signal processing method for Fabry–Perot interferometer is proposed which can be utilized for high-speed dynamic displacement measurements, e.g. mechanical vibration measurements. The lookup table (LUT) integrated with the interference intensity equation has been employed for the interpolation processing of interference signals. With the aid of this method, the interpolation error has been reduced by 40% in comparison with that resulting from the commercial sinusoidal signal processing module. By operations of Fast Fourier Transform (FFT), the displacement measurement distribution can be converted into the frequency spectrum diagram. The interpolation resolution of the proposed interferometric displacement measurement system is about 0.1 nm. Experimental results demonstrate that this interferometer system is available for measuring frequencies till 2 kHz where its corresponding amplitude is 0.15 μm.     

Simplified, ideal or inverted decoupling?

This paper presents a comparative study of simplified, ideal and inverted decoupling. The stability, robustness and implementation of the three decoupling methods are studied. The structured singular value (SSV) is used to carry out some comparisons. It is demonstrated that robust performance and robust stability of a nominally stable control system are equivalent for the three decoupling methods when the controllers are tuned to obtain identical nominal performance. A relation is derived between the presence of right-half plane (RHP) zeros of a process in series with its simplified decoupler and the instability of the ideal and inverted decouplers for the same process. This paper also describes a potential implementation problem related to the particular structure of the inverted decoupling. Finally, a recapitulative table of the main advantages and limitations of each decoupling method is presented.     

Ecological cutting: Feasible or not?

This paper describes the results of a two-year research project on ecological cutting, in which four different applications, namely, cutting, pocket milling, face milling, and drilling, were investigated under dry and lubricated conditions. A traditional cutting fluid and an environmentally friendly cutting fluid were used for the latter. TiN-, Ti (C,N), and (Ti,Al)N-coated tools were tested, together with commercially-available multilayer coated tools, to analyse to what extent the use of coatings could reduce or even eliminate the need for cutting fluids. The machined materials include an unalloyed steel, I.0503, a low alloyed steel, 1.2312, a stainless steel, 1.4306, and cast iron, ADI. End-of- life tests were done in all cases and the wear of the tools was examined with SEM. The research showed that the results are strongly dependent on the application. For cutting, coated tools result in the best tool lives although tools used under lubricated conditions still outperform their dry used counterparts. For milling, dry machining is advantageous. The drilling tests showed better results under lubricated conditions mainly due to the cooling and chip removal capacity of the lubricants. In this case, the (Ti,Al)N-coated drill out-performed the commercially available coated tool.     

Tribological behaviour of antiwear additives used in hydraulic applications: Synergistic or antagonistic with other surface-active additives?

This paper examines the friction and antiwear (AW) properties using SRV (Schwing–Reib–Verschleiss) tribometer and film-forming properties using atomic force microscope (AFM) of one simple model formulation containing solely AW additive and seven oils containing mixture of additives including three zinc-based packages (ZP), ZP with additional AW additives, ZP with extreme pressure (EP) additives, ZP with viscosity index improvers (VII) and one zinc-free ashless package in steel/steel contacts. VII-containing oil show lower boundary and mixed friction coefficients than the other oils. Although all AW additive-containing oils formed tribofilms, AW properties of ZPs appear to be affected antagonistically by EP additives while synergistically by VII. Zn-free additives investigated in this study show higher wear than ZPs.     

Chaos or control? [production planning]

The authors describe a project that used a novel approach to a complex production planning and control requirement. This follows an earlier article that described how finite-capacity planning was simulated using a standard MRP system     

Animal models are reliably mimicking human diseases? A morphological study that compares animal with human NAFLD

Non‐alcoholic fatty liver disease (NAFLD) is a clinical‐pathological syndrome that includes a wide spectrum of morphological alterations. In research, animal models are crucial in evaluating not only the pathogenesis of NAFLD and its progression, but also the therapeutic effects of various agents. Investigations on the ultrastructural features of NAFLD in humans are not copious, due to the difficulty to obtain human samples and to the long time of NAFLD to evolve. Translational comparative studies on the reliability of animal models in representing the histopathologic picture as seen in humans are missing. To overcome this lack of investigations, we compared the ultrastructural NAFLD features of an animal model versus human. Sprague‐Dawley rats were fed with a high fat diet (HFD) for 1–4 weeks, while control rats were fed with a standard diet. Human specimens were collected from patients with diagnosed fatty liver disease, undergoing liver biopsies or surgery. Rat and human samples were examined by light microscopy and by transmission and high resolution scanning electron microscopy. The present work demonstrated that NAFLD in animal model and in human, share overlapping ultrastructural features. In conclusion, animal HFD represent an appropriate tool in studying the pathogenesis of NAFLD. Microsc. Res. Tech. 77:790–796, 2014. © 2014 Wiley Periodicals, Inc.     

新风系统or空气净化器,你该选择谁?

正近几年,空气质量问题已呈不断加剧和周期延长之势,空气问题给人们的身体造成的伤害也越来越大,有人因此而患上咽炎、肺炎,甚至肺癌,这不免让人担忧。那么,就有必要来弄清楚新风系统和空气净化器到底有什么区别?新风系统和空气净化器哪个效果更好?新风系统是抗霾除甲醛的一大利器,它可以将室内的污浊空气经热回收后排向室外,同时可以将室外的新鲜空气经过多层过滤处理后,再进入高效热回收器,然后被持续均匀     

Development of a radiative transfer model for the determination of toxic gases by Fourier transform–infrared spectroscopy with a support vector machine algorithm

Abstract

This report describes a radiative transfer model for Fourier transform-infrared (FT-IR) spectroscopy to create close-to-reality toxic gas spectra by reflecting the unique spectral responses of detectors and using the atmospheric radiative transfer code, MODTRAN. This system can be highly useful in overcoming the limitations for measuring toxic gases in open environments. The emulated gas spectra can be used to train support vector machine (SVM) for chemical gas detection. Its detection performance is evaluated with nerve agents (tabun, sarin, soman, and cyclosarin) and a simulant gas (sulfur hexafluoride) for indoor and outdoor experiments by using two off-the-shelf FT-IR gas detectors. The experimental results show that the proposed SVM algorithm successfully detected and classified targeted gases while reducing false negative and false positive detection rates.