Koch, Ismael E.Klein, IvandroGonzaga, LuizRofatto, Vinicius F....
10页查看更多>>摘要：Estimating the quality of GNSS vectors is decisive in planning GNSS networks and in several land surveying activities. These vectors are indirectly present in many civil infrastructures usually in the first stages of constructions and thus of high importance. In this research we assembled over 1000 baselines producing an extensive database with over 170,000 processed vectors. We propose a novel identification of outlying GNSS vectors based on the Isolation Forest (IF) algorithm based on the vectors deviations. And a new procedure to build linear models based on metaheuristics and a penalty function. The linear regressions presented models with a coefficient of determination R-2 up to 0.996. The observation time span variable remained in all equations at least twice, showing its importance for the outcome quality of a vector. Overall, the threedimensional deviation of vectors processed with broadcast ephemeris is 2.4 times higher than for precise ephemerides.
原文链接:
NSTL
Elsevier
Huang, DawenTang, ShanhuaZhou, DengjiHao, Jiarui...
10页查看更多>>摘要：Nitrogen Oxides (NOx) emission is an inevitable concomitant process of gas turbines operating in industrial scenes. Most of the existing NOx estimation methods have characteristics of strong mechanism dependence, low estimation accuracy and long estimation time, moreover, the parameters used for estimation are not easy to be measured. This work designs a novel neural network model with an adjustable intermediate layer to estimate NOx by taking the ambient and boundary parameters as model inputs to promote engineering applications. The easily measurable outlet temperature of the compressor is selected as the adjustable intermediate parameters to improve estimation accuracy. The proposed model is trained and verified by historical data collected from the various operating conditions of gas turbines. The influences of weight coefficient combinations, relative humidity and intermediate parameter on the NOx estimation accuracy are further analyzed and discussed. The results show that the proposed model has higher estimation accuracy and convincing estimation results compared with the traditional estimation method. Adjusting the intermediate layer parameter can further improve the estimation performance. The estimation accuracy is improved by about 2.23%, and estimation error is reduced by half, which is more suitable for estimating NOx emission of gas turbines in industrial scenarios with smaller sample sizes.
原文链接:- NSTL
- Elsevier
Chen, PengDing, JianguoZhuang, HuiChang, Yu...
15页查看更多>>摘要：The combined influence of manufacturing errors, misalignment and inertia effects on bearing performances is studied. The extended Reynolds equation considering inertia force of compressible air film is derived and solved by streamline upwind Petrov-Galerkin finite element method (SUPG FEM). The theoretical models of manufacturing errors and misalignment are established and verified. The results show that manufacturing errors have a significant impact on bearing performances. The influence of misalignment on moment is great, while the effects on load capacity, radial stiffness and angular stiffness are relatively small. Inertia effects can reduce bearing performances except for the journal with taper error, and the influence of inertia effects on bearing performances could be ignored when the film thickness is less than 20 mu m.
原文链接:- NSTL
- Elsevier
Georgin, E.Peruzzi, A.Bosma, R.Tabandeh, S....
9页查看更多>>摘要：Three European National Metrology Institutes (NMIs), VSL, LNE-CETIAT and INRiM, extended their relative humidity calibration capabilities to temperatures up to 170 degrees C, dew-point temperatures up to 150 degrees C and pressures up to 600 kPa. In order to test the equivalence of the respective calibration set-ups, 4 commercial hightemperature relative humidity sensors were exchanged among the three NMIs and calibrated at different combinations of relative humidity (19 %rh to 70 %rh), air temperature (100 degrees C to 170 degrees C) and pressure (100 kPa to 500 kPa), realizing dew-point temperatures of either 81.5 degrees C or 127 degrees C. The initial and final measurements at VSL showed that the stability of the selected sensors was sufficient for comparing the different calibration set-ups. The results of the comparison showed that VSL and LNE-CETIAT facilities agreed within their claimed uncertainties (<0.3 %rh), while discrepancies of up to 4 %rh were observed between VSL and INRiM facilities.
原文链接:- NSTL
- Elsevier
Zhang, KanghuiWang, WeidongLv, ZiqiJin, Lizhang...
12页查看更多>>摘要：Coal ash content is an important criterion for evaluating coal quality. In recent years, the online ash measurement approach based on a convolutional neural network (CNN) has gotten a lot of attention. However, learning continuous targets from a small and unbalanced dataset is one of the biggest challenges for ash content estimation using CNN. In this paper, a CNN-based regression framework was proposed for rapidly estimating the ash content of coal. Firstly, data synthesis was performed to augment the limited dataset, and label distribution smoothing (LDS) was employed to alleviate the imbalance in datasets. Secondly, separable convolution (SC) and attention modules were introduced into multi-branch (MB) blocks of the backbone. SC was applied to fuse both spatial and channel-wise information, and attention modules were used to enhance feature extraction capability. Finally, as a final estimation value, the regression head outputted a float in the range [0, 100]. The results showed that the proposed approach achieved 0.31% error on the 1,145 test images, where 81.76% had a margin of error less than 0.5% and 96.25% less than 1.0%. Furthermore, the prediction error analysis revealed that the accuracy of the predictions was highly related to the homogeneity of the materials. The visualization results demonstrated that the proposed regression framework could merge multi-scale information and that the synthetic dataset was viable.
原文链接:- NSTL
- Elsevier
Lu, NaLi, MingliangZhang, GuangtaoLi, Ruiqiang...
17页查看更多>>摘要：Fault feature extraction plays an important role in rotating machinery fault diagnosis. With progress in the development of signal processing methods, more and more features can be obtained from rotating machinery signals. However, these often contain many superfluous features, and the commonly used single evaluation criterion in the feature selection procedure is often inadequate for selecting sensitive features. With this problem in mind, a synthetic maximum index, with which both the global and local properties of features can be considered, is proposed for feature selection. Combining this index with the advantages of complete ensemble empirical mode decomposition with adaptive noise and the locality preserving projection algorithm, a novel fault feature extraction method for rotating machinery is proposed. The average fault recognition accuracies of this method on three datasets are 99.79%, 99.17% and 100%, respectively. Comparing it with seven comparative methods, the results demonstrate that the proposed method has better performance.
原文链接:- NSTL
- Elsevier
Grabowski, KrzysztofSrivatsa, ShreyasVashisth, AniruddhMishnaevsky, Leon, Jr....
18页查看更多>>摘要：Structural Health Monitoring (SHM) has a major role to play in the damage identification strategy of engineering structures. Sensors form an integral part of SHM and the development of sensors with minimum effect on measuring physical parameters leads to effective monitoring. The exciting discovery of MXene nanomaterials has made a tremendous impact on the field of sensors for various applications ranging from wearable health sensors to gas sensors. This review paper explores the sensing capabilities of MXene nanomaterials for SHM of engineering structures. MXenes are a family of two-dimensional nanomaterials with carbide or nitride layer (X layer) sandwiched between transition metal layers (M-layer); with more than 100 unique stoichiometric MXene combinations discovered to date, these nanomaterials can achieve wide tunability by varying ratios of M or X layers. Monolayer Titanium Carbide (Ti3C2) MXenes are widely used for sensing applications and these MXenes have 330 +/- 30 GPa modulus, 2.31 +/- 0.57 mu Omega.m electrical resistivity, and 2.6 +/- 0.7 cm(2)V(-1)s(-1) field-electron mobility. The review paper first covers the physical and chemical properties of MXene and MXene composites. Next, various MXene sensors developed in recent years are compared with conventional sensors; for example, Ti3C2-MXene sensors have shown impressive response times as low as 7.13 +/- 1.28 mu s which are comparable to piezoceramic sensors and outperform piezoresistive-type silicon sensors (for similar shocktube experiments). Additionally, recent advances in computational models for MXenes and their nanocomposites are provided to discuss further possibilities of virtual model development for the design of sensors. Sources of uncertainties of both physical sensors and computational models are discussed along with the effect of MXene material properties on measurement concepts like repeatability, reliability, and error estimation, etc., of the sensors. The purpose of reviewing both physical and computational models is to facilitate the use of MXene nanomaterial-based sensors in SHM applications.
原文链接:- NSTL
- Elsevier
Mirzaei, MehranRipka, PavelGrim, VaclavJelinek, Lukas...
20页查看更多>>摘要：This paper presents a way to calculate the shell thickness of nonmagnetic hollow cylinders for nondestructive applications. Aluminum cylinders with a solid structure and with a hollow structure are considered. The motion component of the induced eddy currents in a conductive cylinder is utilized to evaluate the shell thickness of hollow conductive cylinders at various frequencies and at variable speeds. One axisymmetric excitation coil and two axisymmetric pickup coils with antiserial connection are used. An analytical method using an axisymmetric computational model is developed for a parametric analysis of solid and hollow cylinder structures and shell thickness calculations, in which Fourier series are utilized. A 2D axisymmetric finite element method is also performed for a comparison with the results of the analytical method. The measurements at variable speeds and at various frequencies are presented with various hollow aluminum cylinders. The high linearity of the induced voltage versus the speed curve makes it possible to calculate the shell thickness of nonmagnetic hollow cylinders at different speeds.
原文链接:- NSTL
- Elsevier
Min, YazhouShen, ShengnanLi, HuiLiu, Sheng...
9页查看更多>>摘要：Laser-based Directed Energy Deposition (L-DED) is a promising additive manufacturing technology, which has broad application prospects and practical value in many fields. The nondestructive testing technology of L-DED work piece quality monitoring requires high accuracy and capability for real-time process. This work developed an online monitoring system based on a miniature electron impact ion source time-of-flight mass spectrometer (EI-TOF) and a high-speed camera, which monitored the atmosphere above the molten pool area. The number of spatters was measured using a high-speed camera. The composition of the samples and spatters was measured by using element analyzer, inductively coupled plasma mass spectrometry, and electron spectroscopy. The variation in the atmosphere was measured using EI-TOF, and the results confirmed that the O2, N2 and H2O content decreased during the L-DED process. At the laser power of 400 W, the oxygen consumptions were 92.5% and 86.4% compared with those at the laser power of 500 W and 600 W, respectively. During the L-DED process, the number of spatters decreased when the laser power was increased from 400 W to 600 W. And at the laser power of 600 W, the average number of spatters was reduced to 59.3% compared with the laser power of 400 W. It can be found that dust contained a large amount of virgin powder and little spatters. It also can be found that at the laser power of 400 W, 500 W and 600 W, the amount of oxygen in the dust was 0.544%, 0.242% and 0.159%, respectively. The relative content of oxygen in the cross section of the seam was 35.58%, 43.79% and 44.30%, respectively. The deviation of the monitoring results (H2O, N2, O2) are significant at the same power when different materials was used as the substrate.
原文链接:- NSTL
- Elsevier
