The transient components in the early weak fault vibration signals of rolling bearings are easily obscured by intense background noise and cannot be detected quickly. Based on the sparse ...representation principle, an artificial bee colony (ABC) optimization sparsity method of the Laplace wavelet dictionary is proposed to realize the transient characteristic components in the signal extraction. Sparse decomposition with Orthogonal Matching Pursuit (OMP) algorithm is a signal adaptive decomposition algorithm, and it is one of the effective methods for weak feature extraction under strong noise background. Aiming to select and construct an over-complete dictionary for the sparse representation of rolling bearing fault vibration signals, based on the analysis of fault signals' characteristics, an improved Laplace wavelet atomic library was constructed. For solving extensive calculation and low efficiency of the orthogonal matching pursuit algorithm, this paper combines the ABC algorithm's fast operation characteristics to select the improved Laplace wavelet atom that best matches the fault through the inner product operation, thereby improving the calculation efficiency. Experiments show that the method has a proper matching with the early weak fault signals of rolling bearings and can adequately characterize fault information and judge the fault type more accurately.
This paper studies a novel multigrid approach to the solution for a second-order upwind-biased discretization of the convection equation in two dimensions. This approach is based on semi-coarsening ...and well-balanced explicit correction terms, added to coarse-grid operators to maintain on coarse grids the same cross-characteristic interaction as on the target (fine) grid. Multicolor relaxation schemes are used on all the levels, allowing a very efficient parallel implementation. The results of the smoothing analysis and numerical tests can be summarized as follows: (1) The residual asymptotic convergence rate is about 3 per cycle, which far surpasses the theoretical limit (4/3) predicted for standard multigrid algorithms with full-coarsening. (2) The full multigrid (FMG) algorithm with two
V(0,2) cycles on the target grid and just one
V(0,2) cycle on all the coarse grids always provides an approximate solution with the algebraic error less than the discretization error. (3) A novel algorithm for deriving a discrete solution approximating the true continuous solution with a relative accuracy given in advance is developed. The computational complexity of this algorithm is (nearly) optimal (comparable with the complexity of the FMG algorithm applied to solve the problem on the optimally spaced target grid).
In order to clarify the characteristic compounds and establish the authenticity evaluation method of heptapleurum honey, high-performance liquid chromatography coupled with quadrupole-time-of-flight ...tandem mass spectrometry (HPLC-Q/TOF-MS/MS) was used to qualitative and quantitative analysis of characteristic compounds in heptapleurum honey. Five compounds were identified including 4-(1'-cyclodiethyl ether-3'-butanediol)-3,5,5-trimethyl-2-cyclohexenone (Unedone B), 3,4,5-trimethoxy cinnamyl alcohol, 4-(1'2'-dihydroxy-3'epoxypropane) -3,5,5-2-cyclohexenone (Unedone C), trans, trans abscisic acid, and cis, trans abscisic acid. Notably, 3,4,5-trimethoxy cinnamyl alcohol was first found in honey, and it could be a marker of heptapleurum honey. Moreover, 10 raw heptapleurum honey samples with different geographic origins were collected to establish HPLC fingerprint. The authenticity of six commercial heptapleurum honey samples were evaluated by combining characteristic compound with HPLC fingerprint. The results d
•The proposed MTMD method can extract vibration components robustly.•The relationships between mono-trend signal components are utilized.•The mono-trend signal components can be extracted ...simultaneously.•The proposed method can deal with close-spaced components and strong noise.
The analysis of vibration signals of rotating machinery plays an important role in equipment fault diagnosis and health monitoring. However, the decomposition of fault characteristic components often lacks robustness and accuracy under nonstationary operating conditions due to potential strong background noise and the complexity of existing components. In this paper, we address this issue by utilizing the relationships among components of vibration signals generated by rotating structures, described as the mono-trend modes (MTMs). Our proposed method, called the MTM decomposition (MTMD), enables robust feature extraction from vibration signals under nonstationary operating conditions. Initially, the instantaneous angular speed (IAS) of the input shaft is measured by tachometers or estimated by the framework of parameterized resampling time–frequency transform. The instantaneous frequencies (IFs) of the targeted components are then determined based on their orders relative to the IAS. Subsequently, the instantaneous amplitudes (IAs) of the targeted components are estimated by solving a joint optimization problem that includes a penalty term designed in consideration of the low variation characteristic of IAs. This penalty term enhances the efficient distribution of energy among close-spaced components. As a result, all targeted MTMs can be extracted simultaneously without any accumulated error. Various simulated experiments and practical experiments on a high-power planetary gearbox are conducted to analyze and validate the effectiveness of the proposed MTMD method in extracting robust features, especially in the presence of strong noise and close-spaced components.
This paper aims to explore the decomposition characteristics of SF 6 under thermal fault, which can further improve the method of using SF 6 decomposed components to diagnose inner insulation status ...of SF 6 insulated equipment. Hence, the thermal fault simulation system of SF 6 electrical equipment is designed and serials of experiments are conducted. It initially gets SF 6 thermal decomposition characteristic for temperature below 400°C. Then it analyzes decomposed component species and their generation regularity, determines the main characteristic component of SF 6 thermal decomposition and chooses the key component to represent fault severity. The result shows that: SF 6 begins to decompose obviously at 300°C and the main decomposition components contain CO 2 , SO 2 F 2 , SOF 2 , SOF 4 , SO 2 and H 2 S; the improvement of fault temperature will promote the decomposition of SF 6 , but the formation regularity of each decomposed component is different; H 2 S is the special component only appears when thermal fault proceeds to some degree (above 360°C). Hence, decomposed components and their formation regularity can be used to diagnose the SF 6 equipment thermal fault. H 2 S can be used as the key component to represent fault severity.
Volcanic rocks, preserving paleorecords of Earth's magnetic field, are essential to constrain the working of the geodynamo, provided their primary signal was not biased. Using a thermomagnetometer, ...we simulate a situation where a sample's primary record, carried by a thermoremanence (TRM, acquired by cooling in air from 600°C to room temperature), is partly overprinted by a chemical remanence (CRM, acquired by 200 hr of isothermal exposure at 400°C). This situation leads to two directional and intensity components (in the form of linear segments) in the Zijderveld and Arai‐Nagata diagrams. In the case of unstable titanomagnetite grains prior to CRM acquisition, we show that both components can be strongly biased by up to ∼50° for paleodirections and ∼50% for paleointensities. In such a worst‐case scenario, the secondary CRM strongly overprints the primary TRM, rendering the common interpretation of Zijderveld and Arai‐Nagata diagrams in terms of characteristic components invalid.
Plain Language Summary
Volcanic rocks, the magnetic minerals of which can acquire a thermoremanent magnetization (TRM) from Earth's magnetic field during their initial cooling, are essential to constrain the working of the geodynamo through Earth's history. However, if the rock is subsequently reheated at moderate temperature in another ambient field, the initial record can be partly overprinted by a chemical remanence (CRM). Starting from a TRM applied on materials of various thermostability, we reproduced in laboratory conditions the acquisition of a CRM by annealing the rock in a controlled ambient field for 200 hr at 400°C. Rock‐magnetic and structural analyses at regular intervals, supplemented by continuous measurements of the remanent magnetization, indicate the creation of new phases as a result of oxidation processes. The paleomagnetic analysis of the final products reveals the existence of two distinct components that can be associated with the initial TRM and the secondary CRM. Whereas the paleomagnetic record of the initial TRM is trustworthy for the most stabilized initial products, directional (up to 50°) and intensity (up to 50%) biases are observed for the least stabilized initial products, illustrating a critical example where the interpretation of characteristic components (linear segments in the interpretation diagrams) is invalid.
Key Points
We overprint a thermoremanent magnetization (TRM) by cooling from 600°C with a chemical remanent magnetization by 200 hr exposure at 400°C
Chemical remanent magnetization was produced by the creation of cation‐deficient titanomagnetite phases, then stabilized by oxyexsolution
Paleodirections and intensities are strongly biased in the worst scenario, making the interpretation of characteristic components invalid
To obtain relationship between concentration of SF 6 decomposed characteristic components (or their concentration ratio) during the formation process and partial discharge qualities and pulse ...repetition rate, this paper used needle-plate electrode to simulate outthrust insulation fault and conducted a serial of experiments. First, the SF 6 decomposition characteristic under different PD strengths is obtained. Then this paper defines average discharge qualities per second as Q SEC . It considers both apparent discharge qualities and discharge pulse repetition rate, and analyzes the relation feature between SF 6 decomposition characteristic (both concentration of component and their effective formation rates RRMS) and Q SEC . Besides, it proposes C(SO 2 F 2 )/C(SOF 2 ) as the energy characteristic ratio (ER) to represent PD energy, and defines the effective energy characteristic ratio as (ER RMS ). Moreover, it achieves the inner correlation feature between Q SEC and all the characteristic component concentration, the RRMS of each characteristic component and ERRMS. The results show that: since number of C atoms from stainless steel surface and content of trace H 2 O and O 2 in gas chamber were limited, both decomposed component concentration and component concentration ratio accords with the famous "Logistic Population Model" growth trend in ecology, which means they present "S"-curve increase with Q SEC . The proposed ER can effectively indicate the amount of PD energy and the defined ER RMS can objectively reveal the variance regularity of PD energy with Q SEC . Hence, the correlation mathematic formula between ER RMS and Q SEC is obtained and ER RMS can be used as the new characteristic parameter to represent PD energy. It establishes the foundation for the further fault diagnosis research.
Changes in nutraceutical and palatable components of Thai soybean (Chiang-Mai 60, CM60) and black soybean (Sukhothai 3, SK3) were investigated during long-term soaking at 35 °C for 48 h. Isoflavone, ...saponin, free sugar, free amino acid including γ-aminobutyric acid (GABA) and folate, and also antioxidant capacity (H-ORAC) were evaluated. Isoflavone composition in CM60, malonylglycoside and glucoside were degraded to their aglycone forms while components in SK3 did not change greatly during long-term soaking. Total amount of soybean saponins including DDMP-saponins and group B saponins (group B) did not change significantly but the ratio of DDMP-saponins and group B changed; DDMP-saponins decreased while group B increased with soaking longer than 24 h. The soaking process decreased the contents of free sugars; sucrose, stachyose, and raffinose. Total amount of free amino acids in CM60 showed a decreasing tendency especially for amino acid groups showing undesirable bitter taste characteristics after 48 h soaking. GABA increased after 12 h soaking in both samples. Folate content increased up to 12 h soaking but then reduced to the original amount or lower with long-term soaking. Antioxidative activities of SK3 decreased after 24 h soaking. Results showed that long-term soaking affected the amounts of isoflavones, group B saponins, GABA, stachyose, raffinose and folate.
•Nutraceutical and palatable components of Thai yellow and black soybean were studied.•Long-term soaking effects on nutraceuticals in soybeans were newly reported.•Isoflavone and saponin chemical structure were evaluated during long-term soaking.•Free sugar, free amino acid, GABA, folate and antioxidant capacity were investigated.•Changes of taste components in soybeans during long-term soaking were newly reported.
Garlic has been used as a vegetable since ancient times, and it has proved versatility in preventative and therapeutic approaches. The use of garlic in the food business was restricted because of its ...strong flavor and harsh odor. Fermentation and different chemical processes, such as the Millard reaction and microbial fermentation, produce black garlic. Thermal processing at precise temperatures and relative humidity enhanced flavor and prolonged shelf life. This article holds the most up-to-date information about the resourcefulness and complexity of garlic processing and its biological implications. Recent findings have shown proof of the superior qualitative features and physical activities of black garlic. Before introducing this to the food market, researchers must conduct high-quality research to evaluate the changes of metabolites to achieve largest antioxidant, anticancer, anti-obesity, anti-inflammatory, immune, hepatoprotective, cardioprotective, neuroprotective, and anti-allergenic performance. Researchers should evaluate the quality, marketing, post-harvest handling, and consumption practices of black garlic.
•Model compound of bio-oil is selected based on the characteristic components.•Solubilization capacities of characteristic components are quantitatively analyzed.•Polarity significantly affects the ...solubilization capacity of component in diesel.•Influence strength of B/D ratio is weaker than that of surfactant concentration.
In this study, a bio-oil model compound of walnut shell pyrolysis oil was selected. The microemulsions of diesel and model compound were produced using Span80 and Tween 80 as surfactants. The microemulsions were quantificationally analyzed to investigate the solubilization capacity of bio-oil characteristic components in diesel. The effects of surfactant concentration and initial volume ratio of bio-oil model compound to diesel (B/D ratio) on the solubilization capacity of bio-oil characteristic components in diesel were investigated. The heating value, kinematic viscosity, elemental analysis and thermogravimetric analysis of microemulsion were also conducted. Experimental results indicated that the suitable concentration of surfactant was 0.3 mol/L–0.45 mol/L, and the optimum B/D ratio was 4:12 for the bio-oil model compound. The dissolubility of m-cresol and guaiacol in microemulsion was much better than that of water and acetic acid. The heating value and the kinematic viscosity of microemulsion decreased slightly as the B/D ratio increased. Increasing the surfactant concentration contributed to a more pronounced increase in the kinetic viscosity and a significant decrease in the heating value. The influence of surfactant concentration on the fuel properties and thermogravimetric characteristics was stronger than that of B/D ratio.
