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In modern tunnel construction, TBM (Tunnel Boring Machine) plays a very important role. In response to the needs of tunnel wall reinforcement and TBM automated construction for tunnel construction, a shotcrete mechanism mounted on the TBM is designed. In order to evaluate the kinematic performance of the mechanism, this paper studies the forward and inverse kinematics and spatial architecture of the TBM shotcrete robot. Firstly, based on the D–H parameter method, the number of joints and links is determined and structural analysis is performed to obtain the robot's forward kinematics equation, achieving the mapping between joint space and pose space. Then, by determining the joint variables, the mapping of the end tool in Cartesian space is achieved. Finally, based on the Monte Carlo random sampling method, the workspace of the robot is constructed, and its reachability and flexibility within the robot workspace are evaluated. The performance of the device is verified by building a prototype, which meets the requirements well. Through the research in this paper, it can provide theoretical basis and guidance for the design and control of the shotcrete robot. [ABSTRACT FROM AUTHOR]

The ring-shaped electrostatic sensor is a typical particulate flow measurement system, which suffers from flow profile dependency due to its non-uniform spatial sensitivity. In this paper, a method based on sensor's output power frequency spectrum is proposed, which can be realized by repeatedly decomposing the sensor's overall output power spectrum to identify elementary frequency spectra corresponding to equivalent flow streams. The decomposed components can then be re-weighed to improve the uniformity of spatial sensitivity. This is a low cost approach, and there is no need to modify simple structure of the current sensor. The figure below shows an example of the power spectral responses due to flow streams in different radial paths and the resultant overall power spectrum noted as Overall 1. The grey graph represents the spectrum generated by the outmost layer of flow stream. The tail of Overall 1 effectively coincides with that of grey graph. Based on this phenomenon, from the tail of Overall 1, the grey graph can be identified. By stripping off the grey coloured component, a new tail will appear in a new Overall spectrum. This process is repeated until the innermost layer is identified. Each identified spectral component is then reweighted to achieve a uniform spatial sensitivity. Image 1 • A flow of constant rate produces a smaller signal when passing pipe central line than travelling near pipe wall. • The proposed method is to tackle the above problem. • Experiments and simulation confirm the "tail" of the sensor's output is dominated by the response to outmost layer flow. • Hence "Tail", i.e. the high frequency part output power spectrum can be used to identify the outmost layer of flow. • Stripping off outmost layer, the next layer will be exposed. • By repeating the same procedure, until the innermost layer of the spectrum is identified. • By re-weighting the decomposed spectra, the same flow stream will achieve the same output wherever the stream passes. [ABSTRACT FROM AUTHOR]

The ring-shaped electrostatic sensor is a gas–solid flow measurement system, which has a problem of flow profile dependency. To deal with this problem, a method was introduced in this paper, which was to repeatedly use the successive "tails" of the sensor's overall output power spectrum to identify elementary frequency components corresponding to the equivalent roping flow streams. From the radial locations of these equivalent flow streams, the decomposed power frequency spectral components were then reweighted accordingly. Through such signal processing, an improved electrostatic sensor spatial sensitivity was achieved without modifying the sensor's structure. The method of interpolation was presented and discussed, and the effect of velocity profile on the proposed method was evaluated under different velocity profiles. [ABSTRACT FROM AUTHOR]

Real-time and accurate flue gas temperature and velocity measurement is crucial for the safety, efficiency, and low emission of a power plant operation. This article describes a new technique for measuring flue gas temperature and velocity based on acoustic frequency division multiplexing (FDM) in a simultaneous way. The FDM method provides a technique that allows the simultaneous utilization of multiple acoustic signals that leads to a greatly reduced measurement cycle time required; therefore, the measurement system’s temporal resolution is significantly improved. With this new FDM method, the composite signal formed of two channels’ is decomposed by using a Butterworth filter for the extraction of the amplitude and phase information of signals passing each of the individual channels. From the derived frequency signals, the time of flight (TOF) on each acoustic path can be obtained. Demonstrated through both a theoretical analysis and experimental results, by applying the new technique, the measurement period can be reduced to 0.083 times (or say less than 10%) of that by using a traditional method. At the same time, the experimental results indicate that the new technique also improves the accuracy of the measurements. The sensitivity of the FDM method is 3.3, and 2.6 times higher than that of the HWA and traditional methods for velocity, and 1.6 and 1.4 times higher for temperature measurement. Moreover, its optimal robustness and precision are verified by several combined experiments with and without wind with background noise. [ABSTRACT FROM AUTHOR]

Temperature and humidity coupling has a more significant effect on the failure properties of bonded joints than a single factor, and there is not enough research on this. In this paper, joints bonded with strong toughness structural adhesives are selected for the experimental analysis of joints aged for 240 h, 480 h, and 720 h at temperatures of 40 °C and 60 °C and a humidity of 95% and 100%. The sequential double Fick's model was used to fit the water absorption of the joints, and the comparison yielded that the water absorption of the adhesive was in accordance with Fick's law. The quasi-static tensile tests revealed that the reduction in mechanical properties of the joints was positively correlated with the moisture content in the environment, while the competing mechanisms of post-temperature curing and hydroplasticization resulted in a slight increase in the failure strength and energy uptake of the aged joints, which is in agreement with the experimental results of the Fourier infrared spectroscopy. A combination of macroscopic failure sections and scanning electron microscope (SEM) images yielded that the failure mode of the joints changed from cohesive failure to interfacial failure with increasing ageing time. In addition, reliability analyses for the fatigue testing of joints are expected to provide guidance for the life design of bonding technology in the vehicle service temperature range. [ABSTRACT FROM AUTHOR]

Accurate ranging and real-time temperature monitoring are essential for metrology and safety in electrical conduit applications. This paper proposes an acoustic time-of-flight (TOF) estimation method based on the digital lock-in filtering (DLF) technique for conduit ranging and thermometry. The method establishes the relationship between the frequency and the time domain by applying a linear frequency modulated Chirp signal as the sound source and using the DLF technique to extract the first harmonic of the characteristic frequencies of the transmitted and received signals. Acoustic TOF estimation in the conduit is then achieved by calculating the mathematical expectation of the time difference between each characteristic frequency in the time-frequency relationship of the two signals. The experimental results with enhanced noise interference on different conduit lengths and various temperature conditions, proved that the proposed DLF method can establish a robust linear time-frequency relationship according to the characteristics of the Chirp signal, and the measurement accuracy of TOF has also been confirmed. Compared to the conventional method, the DLF method provides the lowest absolute error and standard deviation for both distance and temperature measurements with an enhanced robustness. [ABSTRACT FROM AUTHOR]

• A rapid method for obtaining the integrated absorption area was introduced for laser absorption spectroscopy tomography. • The method is applied for the first time to the temperature concentration reconstruction of non-uniform complex combustion flames. • This method has been validated via numerical simulations and field experiments on afterburner flames. • Compared with conventional method, the computational efficiency is improved significantly by at least two orders of magnitude. Laser absorption spectroscopy tomography is widely applied to measure the two-dimensional distribution information in complex combustion flow fields. Rapid and accurate estimation of the integrated absorption area (IA) is the key to achieving accurate online reconstruction. In this paper, a novel method is introduced with the wavelength modulation spectroscopy (WMS) for obtaining the IA, which is applied in the reconstruction of temperature and species concentrations distributions of non-uniform complex combustion flames. With this method, the traditional time-consuming line-shape fitting process is no longer required, and the IA is obtained through simple algebraic operations instead. This method has been validated via numerical simulations and field experiments on afterburner flames. The experimental results show that the measurement accuracy is comparable to that achieved with the conventional WMS with line-shape fitting (WMS-F), however the computational efficiency is improved significantly by at least two orders of magnitude, demonstrating its potential for real industrial applications, where often rapid reconstructions are desirable or required. [ABSTRACT FROM AUTHOR]

3-D soot temperature and volume fraction reconstruction of afterburner flame has been based on spectrally resolved measurement methods and inverse problem theory. So far, the Convolutional Neural Networks (CNN) has been widely used in solving inverse problems to realize real-time reconstruction. However, the convolution and pooling operation can cause erroneous accumulation when dealing with high precision and high mesh density 3-D reconstruction applications. To address this problem, the autoencoder long-short-term-memory (LSTM) neural network and the synthetic dataset considering the interior and exterior parameters of camera are adopted to realize rapid, accurate, and simultaneous reconstructions of the soot temperature and volume fraction of afterburner flame. This method, named StfNet-3D by the authors, is investigated regarding its reconstruction accuracy, noise immunity, and computational costs by comparing that with the CNN, LSTM, and traditional 3-D reconstruction method (3D TVR) through simulations and real-time experiments. [ABSTRACT FROM AUTHOR]

• The proposed method is an acoustic time-of-flight estimation method based on digital locking filtering. • This method can be applied to the non-contact measurement of temperature and velocity of gaseous media. • The proposed method can be applied to acoustic TOF estimation in intensely noisy environments. • High measurement accuracy and stability. • The acoustic source signal is just analyzed once through the proposed method at the initiation of the system. Acoustic thermometry and velocimetry are widely recognized as promising methods for in situ measurement of gas temperature and velocity due to their non-invasive, low-cost, and high-resolution advantages. Accurate estimation of acoustic time-of-flight (TOF) is the key to improving the accuracy of acoustic thermometers and velocimeters. In this paper, a new TOF estimation method is developed based on the digital lock-in filtering (DLF) technique. The signal source is an audible sound with linearly modulated frequencies, and the relationship between the time and frequency domains of the signal is established using digital lock-in and low-pass filtering techniques. The linearity of the time–frequency series and the accuracy of the TOF are improved by using a least-squares-based linear fitting method. Experimental studies of gas temperature and velocity measurements with acoustic methods in static, dynamic, and different signal-to-noise ratio (SNR) environments have been carried out. The DLF method performs well in terms of accuracy and robustness to extract the modulated signals of known carriers in a strong noise environment. Furthermore, the very nature of the method predisposes the time-domain data of the acoustic source signal not to be repeatedly processed at each TOF calculation, which saves system resources for processing the source signal. [ABSTRACT FROM AUTHOR]