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Accurate and rapid recognition of fruit is the guarantee of intelligent persimmon picking. Given the changes in the light and occlusion conditions in a natural environment, this study developed a detection method based on the improved YOLOv5 model. This approach has several critical steps, including optimizing the loss function based on the traditional YOLOv5, combining the centralized feature pyramid (CFP), integrating the convolutional block attention module (CBAM), and adding a small target detection layer. Images of ripe and unripe persimmons were collected from fruit trees. These images were preprocessed to enhance the contrast, and they were then extended by means of image enhancement to increase the robustness of the network. To test the proposed method, several experiments, including detection and comparative experiments, were conducted. From the detection experiments, persimmons in a natural environment could be detected successfully using the proposed model, with the accuracy rate reaching 92.69%, the recall rate reaching 94.05%, and the average accuracy rate reaching 95.53%. Furthermore, from the comparison experiments, the proposed model performed better than the traditional YOLOv5 and single-shot multibox detector (SSD) models, improving the detection accuracy while reducing the leak detection and false detection rate. These findings provide some references for the automatic picking of persimmons.

An elastic solid polymer electrolyte is developed based on the unique properties of triallyl cyanurate, which is beneficial for fast lithium-ion conduction and preventing the combustion of polymer electrolyte.

The aluminum matrix composites (AlB2+α-Al2O3)/Al were fabricated by in situ reaction synthesis from an Al-B2O3 system. The reaction pathways, apparent activation energies and tensile properties were analyzed by using differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), and equipped energy dispersive spectroscopy (EDS). The results showed that there are two-step reactions in the Al-B2O3 system. The first-step is 15Al+7B2O3→7α-Al2O3+AlB12+2B and the second-step is 2B+AlB12+6Al→7AlB2. Their corresponding apparent activation energies are 352 and 444 kJ/mol, respectively. The tensile strength and elongation rate of the composites are 190.5 MPa and 6.6%, respectively.Compared with ordinary aluminum base material, the performance is superior. There are many dimple and cracked α-Al2O3 reinforcements in tensile fracture surface layer.

The phase-based motion magnification technique can exaggerate specific structural vibrations and obtain potential applications in visualizing and understanding modal shapes. However, the quality of motion magnification is affected by noise and clipping artifacts, especially in large amplifications. We propose a hybrid-driven motion magnification framework that combines Eulerian and Lagrangian motion processing. Since the structural global spatial vibration corresponding to different modal shapes usually accumulates energy differences in the timeline, from a Eulerian perspective, temporal intensity variations are denoised and separated according to the energy distribution to control spatial motions. Meanwhile, from a Lagrangian perspective, the motion magnification is realized by compensating spatial motion according to the magnified inter-frame motion vector field. By utilizing both Eulerian and Lagrangian motion processing, the proposed framework supports a larger amplification factor and achieves better performance in perceiving subtle vibrations in controlled modal tests.

Anisomycin (compound 1), a pyrrolidine antibiotic, exhibits diverse biological and pharmacologic activities. The biosynthetic gene cluster of compound 1 has been identified previously, and the multistep assembly of the core benzylpyrrolidine scaffold was characterized. However, enzymatic modifications, such as acylation, involved in compound 1 biosynthesis are unknown. In this study, the genetic manipulation of aniI proved that it encoded an indispensable acetyltransferase for compound 1 biosynthesis. Bioinformatics analysis suggested AniI as a member of maltose (MAT) and galactoside O-acetyltransferases (GAT) with C-terminal left-handed parallel beta-helix (LbH) subdomain, which were referred to as LbH-MAT-GAT sugar O-acetyltransferases. However, the biochemical assay identified that its target site was the hydroxyl group of the pyrrolidine ring. AniI was found to be tolerant of acyl donors with different chain lengths for the biosynthesis of compound 1 and derivatives 12 and 13 with butyryl and isovaleryl groups, respectively. Meanwhile, it showed comparable activity toward biosynthetic intermediates and synthesized analogues, suggesting promiscuity to the pyrrolidine ring structure of compound 1. These data may inspire new viable synthetic routes for the construction of more complex pyrrolidine ring scaffolds in compound 1. Finally, the overexpression of aniI under the control of strong promoters contributed to the higher productivities of compound 1 and its analogues. These findings reported here not only improve the understanding of anisomycin biosynthesis but also expand the substrate scope of O-acetyltransferase working on the pyrrolidine ring and pave the way for future metabolic engineering construction of high-yield strains. IMPORTANCE Acylation is an important tailoring reaction during natural product biosynthesis. Acylation could increase the structural diversity and affect the chemical stability, volatility, biological activity, and even the cellular localization of specialized compounds. Many acetyltransferases have been reported in natural product biosynthesis. The typical example of the LbH-MAT-GAT sugar O-acetyltransferase subfamily was reported to catalyze the coenzyme A (CoA)-dependent acetylation of the 6-hydroxyl group of sugars. However, no protein of this family has been characterized to acetylate a nonsugar secondary metabolic product. Here, AniI was found to catalyze the acylation of the hydroxyl group of the pyrrolidine ring and be tolerant of diverse acyl donors and acceptors, which made the biosynthesis more efficient and exclusive for biosynthesis of compound 1 and its derivatives. Moreover, the overexpression of aniI serves as a successful example of genetic manipulation of a modification gene for the high production of final products and might set the stage for future metabolic engineering.

To study single-tunnel fires in concrete immersed tunnels, a fire test was carried out on a concrete immersed tunnel with a longitudinal length of 5.8 m and a large scale of 1:5. Through self-developed heating and cooling systems and an external load provided by a self-balancing reaction frame, we investigated the temperature distribution, spalling degree, crack distribution, deformation performance, and acoustic emission features of the model. The results showed that both the deformation and cracking of the tunnel exposed to the fire exerted an influence on the unexposed tunnel. Impacted by the single-tunnel fire, the cracks in the immersed tunnel were composed of mainly circumferential and longitudinal cracks, the former of which were connected to each other in places without stirrups. Based on an analysis of the basic AE parameters and the results obtained by a three-dimensional scanner, the spalling of the concrete was caused by different mechanisms, and the maximum spalling depth was 110 mm.

Al–4Cu alloy matrix composites reinforced with TiB2 particles are synthesized by microwave heating (MH). The effects of this heating method (as compared to conventional heating (CH)) and the volume fraction of reinforcements on the microstructure and mechanical properties of the composite samples were studied. Assisted by differential scanning calorimetry (DSC) analysis, the thermodynamics and kinetics of the two methods were discussed, respectively. The results showed that the activation energy for TiB2 formation was 33.8 kJ/mol by MH, against 113.8 kJ/mol by CH, suggesting that the microwave sintering facilitated the reaction process. Moreover, as compared to the CH samples, the ultimate tensile strength (UTS) of the composites prepared by MH method was greater and its value increased with TiB2 content at the expense of percent elongation. The UTS increases from 194.1 MPa to 329.1 MPa and the elongation decreases from 13.70% to 6.26%.

The damage caused by fire can seriously affect the durability and safety of an immersed tunnel, including the reduction of structural bearing capacity and the spalling and cracking of concrete. Fire resistive coating is one of the usual measures to protect the tunnel from fire. In this study, a large-scale (1/5) immersed tunnel was built to carry out a fire test of the immersed tunnel under the protection of fire resistive coating. During the fire test, the heating phase lasted for 365 min, and the cooling phase lasted for 120 min. In the heating phase, the average temperature of the fire in the tunnel reached 1113.7 °C. Under the protection of fire resistive coating, the maximum concrete temperature was 412.4 °C, which was 701.3 °C lower than the average temperature of the fire. During the fire test, the deformations of the tunnel were very small, and the maximum deformation was 6.8 mm. But the concrete cracked seriously on the outside of the tunnel under fire, and the maximum crack width reached 1.86 mm. The concrete cracking not only occurred in the right tube which was exposed to fire, but also occurred in the mid gallery and left tube which were not exposed to fire. According to the temperature of vapor and water in the cracks on the ceiling recorded by the infrared thermography, it was inferred that the depth of cracks in the ceiling had reached 18 cm at 245 min. The acoustic emission signals show that the concrete cracks were mainly formed in the early stage of the fire test (the first 100 min), which is consistent with the macro phenomena of cracks development. The results of the fire test indicate that under the protection of fire resistive coating, the concrete temperatures were high and there was no concrete spalling, and the deformations of the tunnel were small, but the concrete cracking of the tunnel was very serious. Because the immersed tunnel is buried in the seabed, concrete cracks have a great impact on the durability and safety of the immersed tunnel. In the fire resistance design of the immersed tunnel, more attention should be paid to the concrete cracking of the immersed tunnel.

The objective of this study is to clarify the differences of tractive performances generated by the sandy loam-grouser system and the clay soil-grouser system. The tractive performances of the grouser/track shoes are widely researched by previous researchers. However, it is essential to illustrate the influences of the soil properties on the tractive performances of the grouser shoe. Sandy loam and clay soil were used as the test soils for investigating soil parameters in this study. Moisture contents of soil were from 7.5% to 27%, dry basis. Parameters of sandy loam were obtained through direct shear tests, penetration tests, bulk density, and moisture content measurements in laboratory. The grouser shoe was made of steel. Based on the prediction result of tractive performances, the clay soil will always be performed better than the sandy loam no matter which dimension was chosen for single grouser shoe. Based on the experimental results, the grouser height of the track should be 5 cm in order to provide enough traction force, if a tracked vehicle is operated on the environment of either clay soil or sandy loam.

As one of the most reliable motion estimation algorithms that apply phase correlation methods, the single-step DFT (SSDFT) approach has superior characteristics, including the high accuracy and low complexity. However, this approach is limited by the accuracy of the initial estimation. Therefore, it is an enormous challenge to reduce the dimension of the searching area in the subsequent refinement step. As a result, this algorithm is inefficient with large upsampling factors. In order to overcome this problem, an improved two-step image registration algorithm is proposed in the present study. In the first step, the accuracy of the initial estimation is improved by using a motion amplified cross-correlation function. The improved initial estimation is then amended to ensure that retained error is eliminated. In the refinement step, the dimension of the searching area is effectively reduced in accordance with the improved initial estimation and upsampling factor. Obtained results show that for large upsampling factors, the modified SSDFT achieves the same subpixel accuracy as the original algorithm. Meanwhile, it is found that the modified scheme remarkably reduces the computational expense. Finally, conducted experiments on high-speed video sequences demonstrate that the proposed modifications significantly reduce the required time for high precision target tracking tasks.

The lifetime of the sound barrier is threatened by high-speed train-induced impulsive wind pressure as it passes by. The vibration response of the sound barrier during the process of train passing is difficult to be measured using conventional measurement methods because of the inconvenience of the installation of markers on the sound barrier. In this paper, the high-speed camera is used to record the whole process of the train passing by the sound barrier. Then, a displacement extraction algorithm based on the theory of Taylor expansion is proposed to obtain the vibration response curve. Compared with the result simulated by using the finite element method, the video extraction result shows the same head wave and tail wave phenomenon, demonstrating that the vibration measurement by using the high-speed imaging technology is an effective measuring way. It can achieve noncontact and remote vibration measurement and has important practical value.

Al-4Cu alloy matrix composites reinforced in-situ by TiC particulates were prepared by microwave heating (MH) and conventional heating (CH). The samples were heated up to 1273 K in vacuum induction melting furnace and vacuum microwave heating furnace, respectively. The thermodynamics and dynamics associated with the two systems were discussed and the activation energy related to two heating methods was also calculated. The influence of microwave heating on chemical reaction was analyzed. The results showed that Al reacted with Ti to form TiAl3 and carbon atom then displaced Al in TiAl3 to form TiC. The activation energy of TiC reaction generated by MH and CH were 41.4 kJ/mol and 270.0 kJ/mol, respectively. The ultimate tensile strength increased with the increase of TiC volume fraction. In addition, the ultimate tensile strength of the composite prepared by MH was higher than that of the sample prepared by CH.

Carbon Storage Estimation of wood products is one of the important directions of international climate change. As a building material of ecological sustainable development, wood structure building has many advantages, and its performance is better than other structures in many aspects. Forest products are sustainable. If forest products come from sustainably managed forests, and if they follow some principles of sustainable management, then wood, as a material and a product of wood products in daily life, is far more sustainable than other materials, from buildings to furniture. In this paper, the wood structure building is briefly introduced. On this basis, the role of wood structure product carbon flow in forest carbon storage and the impact on the environment are elaborated, which points out the direction for the development of related research in the future. The results are as follows: wood has little impact on climate in the whole life cycle and beyond, and its carbon emission in the life cycle is far lower than that of traditional building materials. The performance of wood structure building constructed with wood building materials is better than that of reinforced concrete structure in terms of energy saving, earthquake resistance, environmental protection and durability. The external ecological environment has a certain positive impact, promoting the sustainable development of society and the harmonious coexistence of man and nature.

This paper reports the results of an experimental study on fire protection performance of intumescent coatings exposed to three non-standard fire curves. Intumescent coatings were applied to steel plates to make test specimens and, in total, furnace tests were performed on 36 specimens. The effective thermal conductivities of the intumescent coatings were calculated based on the measured steel and furnace temperatures. Scanning electron microscopy (SEM) tests were conducted to give some information on the difference in inner structure of intumescent char. Results of the experimental studies reveal that the fire protection performance of intumescent coating is highly dependent on the heating rate and maximum temperature of the fire condition. Different pore structures of the intumescent chars were obtained when intumescent coatings were subjected to fires with varied heating rates. The reaction steps of intumescent coating underwent depended on the maximum temperature of the fire condition. The consequence of this is changed expansion ratio and inner structure of intumescent char and then different effective thermal conductivity. When subjected to non-standard fire I, the reaction process of intumescent coating was incomplete and no “honeycomb” pore structure was observed; in comparison, the coating underwent complete reaction process and compact “honeycomb” pore structure was obtained when exposed to non-standard fire III; the maximum difference for representative values of effective thermal conductivities was up to 48.8%. In addition, due to the peculiar flame retardant mechanism of the intumescent coating, increasing the coating thickness does not always yield insulating property benefit.

This paper presents two tests of full-scale simply supported two-way concrete slabs in a high-temperature environment, based on the standard temperature–time curve (ISO 834). Details of the support conditions, the reinforcement arrangements and the positions of displacement transducers and thermocouple trees are given. Crack development, the temperature distribution, central vertical deflection and edge horizontal deflection of the concrete slabs were recorded during the tests. It was observed that, despite large deflection, neither slab collapsed; this was due to the significant influence of tensile membrane effects on maintaining the structural stability of the floor slabs under fire conditions. Based on the experimental results, an energy-based model to determine the limit load-carrying capacity of concrete slabs at elevated temperatures is verified and discussed. A comparison of the energy-based model results and the test results showed good agreement, while conventional yield theory provides conservative critical reinforcement temperatures in the slabs.

In our study, a deviation extraction method is introduced to obtain subtle deviation signals from structural idealized edge profiles. The deviations are employed to reconstruct an analysis matrix that consists of global translations along selected edge profiles, and then a singular value decomposition-based approach is proposed to extract valuable variations from the calculated analysis matrix. To avoid noises from textured edge profiles, a colorization optimization approach is applied to remove variations because of the textures and turn real image stripes into ones that satisfy the constant edge profile assumption more closely in the deviation extraction process. Two practical experiments are conducted to demonstrate the effectiveness and potential applications of our proposed method. The dynamic properties of a lightweight beam and a sound barrier are analyzed successfully by using high-speed videos.

This note reports an efficient singular value decomposition (SVD)-based vibration extraction approach that recovers sound information in silent high-speed video. A high-speed camera of which frame rates are in the range of 2 kHz–10 kHz is applied to film the vibrating objects. Sub-images cut from video frames are transformed into column vectors and then reconstructed to a new matrix. The SVD of the new matrix produces orthonormal image bases (OIBs) and image projections onto specific OIB can be recovered as understandable acoustical signals. Standard frequencies of 256 Hz and 512 Hz tuning forks are extracted offline from their vibrating surfaces and a 3.35 s speech signal is recovered online from a piece of paper that is stimulated by sound waves within 1 min.

The experimental results of three full-scale two-story, two-bay, composite steel frames under furnace loading are described briefly. During tests, the composite beams and steel columns were exposed to fire, and only the beam-to-column connections of the tested frames were protected. The furnace temperature, composite steel beam temperature, steel column temperature, horizontal displacements of the columns, and vertical deflections of the composite beams as well as the complete deformation process of the test frames observed during the heating phase and the cooling phase are given. By introducing the slope-deflection equations and joint equilibrium conditions at each joint, the critical temperatures of the buckling of two-story, two-bay, composite steel frames are determined for different furnace scenarios; therefore, this method can consider the effect of the axial force at different levels. The calculated critical temperatures agree well with the experimental results.

This paper addresses on the problem of vibration suppression of the Forklift Steering System by active means, which is also proved by the field test Based solely upon the measured vibration data and the Pro/Engineer and Pro/Mechanic finite element modal analysis, there is no need to evaluate or know the system parameters such as mass, damping and stiffness terms. One only need to know the one-to-one correspondence between eigenvalues and a few specific structure parts. Structure modification is equivalent to system eigenvalues changing. Using the parametric design and partial pole placement method, a few undesired eigenvalues of matrix are reassigned suitably in condition of keeping the other eigenvalues unchanged. Then we can assign the resonance peak to a prescribed value. As a result, the vibration amplitude is effectively suppressed and the dynamic characteristics are obviously improved.

This article describes the application of the receptance method vibration control technique on the steering wheel system of a forklift. Numerous advantages of the receptance method over conventional matrix methods as there is no need to know or to evaluate the M, K, C matrix since the determinant of the controller gains are expressed in terms of the receptance measured through experiment. With this method, several poles in the steering wheel system of a forklift which may produce resonance at idle speed of the engine were replaced to predetermined value. Model computation and simulation were carried out with PRO/E software and controllers were implemented using Matlb/Simulink. Locations of the open- and closed-loop poles in the complex plane are obtained to verify that the required assignment of poles had taken place.

High-speed cameras provide full field measurement of structure motions and have been applied in nondestructive testing and noncontact structure monitoring. Recently, a phase-based method has been proposed to extract sound-induced vibrations from phase variations in videos, and this method provides insights into the study of remote sound surveillance and material analysis. An efficient singular value decomposition (SVD)-based approach is introduced to detect sound-induced subtle motions from pixel intensities in silent high-speed videos. A high-speed camera is initially applied to capture a video of the vibrating objects stimulated by sound fluctuations. Then, subimages collected from a small region on the captured video are reshaped into vectors and reconstructed to form a matrix. Orthonormal image bases (OIBs) are obtained from the SVD of the matrix; available vibration signal can then be obtained by projecting subsequent subimages onto specific OIBs. A simulation test is initiated to validate the effectiveness and efficiency of the proposed method. Two experiments are conducted to demonstrate the potential applications in sound recovery and material analysis. Results show that the proposed method efficiently detects subtle motions from the video.

The development of image sensors and optics lenses has contributed to the rapidly increasing use of vision-based methods as noncontact measurement methods in many areas. A high-speed camera system is developed to realize the displacement measurement in real time. Conventional visual measurement algorithms are commonly subjected to various shortcomings, such as complex processes, multiparameter adjustments, or integer-pixel accuracy. Inspired from the combination of block-matching algorithm and simplified optical flow, a motion estimation algorithm that uses modified Taylor approximation is proposed and applied to the vision sensor system. Simplifying integer-pixel searching with a rounding-iterative operation enables the modified algorithm to rapidly accomplish one displacement extraction within 1 ms and yield satisfactory subpixel accuracy. The performance of the vision sensor is evaluated through a simulation test and two experiments on a grating ruler motion platform and a steering wheel system of a forklift. Experimental results show that the developed vision sensor can extract accurate displacement signals and accomplish the vibration measurement of engineering structures.

Rotational angle and speed are important parameters for condition monitoring and fault diagnosis of rotating machineries, and their measurement is useful in precision machining and early warning of faults. In this study, a novel vision-based measurement algorithm is proposed to complete this task. A high-speed camera is first used to capture the video of the rotational object. To extract the rotational angle, the template-based Lucas-Kanade algorithm is introduced to complete motion tracking by aligning the template image in the video sequence. Given the special case of nonplanar surface of the cylinder object, a nonlinear transformation is designed for modeling the rotation tracking. In spite of the unconventional and complex form, the transformation can realize angle extraction concisely with only one parameter. A simulation is then conducted to verify the tracking effect, and a practical tracking strategy is further proposed to track consecutively the video sequence. Based on the proposed algorithm, instantaneous rotational speed (IRS) can be measured accurately and efficiently. Finally, the effectiveness of the proposed algorithm is verified on a brushless direct current motor test rig through the comparison with results obtained by the microphone. Experimental results demonstrate that the proposed algorithm can extract accurately rotational angles and can measure IRS with the advantage of noncontact and effectiveness.

The development of image sensor and optics enables the application of vision-based techniques to the non-contact dynamic vibration analysis of large-scale structures. As an emerging technology, a vision-based approach allows for remote measuring and does not bring any additional mass to the measuring object compared with traditional contact measurements. In this study, a high-speed vision-based sensor system is developed to extract structure vibration signals in real time. A fast motion extraction algorithm is required for this system because the maximum sampling frequency of the charge-coupled device (CCD) sensor can reach up to 1000 Hz. Two efficient subpixel level motion extraction algorithms, namely the modified Taylor approximation refinement algorithm and the localization refinement algorithm, are integrated into the proposed vision sensor. Quantitative analysis shows that both of the two modified algorithms are at least five times faster than conventional upsampled cross-correlation approaches and achieve satisfactory error performance. The practicability of the developed sensor is evaluated by an experiment in a laboratory environment and a field test. Experimental results indicate that the developed high-speed vision-based sensor system can extract accurate dynamic structure vibration signals by tracking either artificial targets or natural features.