摘要 ：

Despite their crucial importance for marine engineering, the nonlinear seismic response characteristics of offshore sites remain poorly understood. Consequently, simulating ground-motion at offshore sites poses a significant challenge. To address this, this study begins with a dataset comprising stress drops of 70 earthquakes, region-specific quality factors, and linear site amplification factors (AFs) of six offshore stations in Sagami Bay, Japan, obtained using the generalized inversion technique (GIT). Then, by incorporating additional offshore accelerograms with focal depths up to 333 km and peak ground accelerations (PGAs) ranging from 0.2 to 4.2 m/s2, we delve deeper into the effects of nonlinear site behaviors on the high-frequency attenuation parameter (κ0) and AFs, respectively. A counterintuitive decrease in κ0 was observed as the peak ground acceleration (PGA) reached 0.5–0.8 m/s2, echoing similar observations from previous studies on KiK-net stations. Our results indicate that the high-frequency attenuation characteristics of offshore sites vary under strong motions, potentially attributable to the nonlinear evolution of the frequency-independent quality factor and S-wave velocity within near-surface sediments. Additionally, the degree of nonlinearity (DNL) at these offshore stations exceeded 4 when PGA reached 0.2–0.3 m/s2, a threshold significantly lower than the previously reported range of 0.5–1.0 m/s2. Furthermore, we observed systematic variations in nonlinear behaviors between flat and steep offshore stations, particularly with peak frequencies shifting towards lower and higher frequencies, respectively. These new findings may be mainly attributed to the intricate interaction of topography and marine sediments. Finally, simulations of two subduction earthquakes (MW6.2 and 5.9) using the stochastic finite-fault simulation method (SFFSM) showed good agreement with observations at frequencies above 0.1 Hz. Notably, nonlinear AFs outperformed linear ones across a wide PGA range of 0.2–1.2 m/s2, highlighting the significance of nonlinear site behaviors in characterizing offshore ground-motions. This finding reinforces the potential of the simulation framework (integrating GIT and SFFSM) for effectively and accurately simulating offshore ground-motion. © 2024 Elsevier Ltd

关键词 ：

Earthquake effects Marine engineering Seismic waves Stochastic models Seismic response Error correction Shear waves

引用：

复制并粘贴一种已设定好的引用格式，或利用其中一个链接导入到文献管理软件中。

摘要 ：

Contact stiffness and backlash in the harmonic drive significantly impact a robot's positioning accuracy and vibration characteristics. The height of the harmonic drive tooth pair is typically less than 1 mm, making the measurement and modeling of backlash and contact stiffness inherently complex. This paper proposes a contact stiffness and backlash model by establishing a correlation between fractal parameters and tooth contact load. To obtain the fractal roughness parameters of the real machined tooth surface, a combination of a noncontact optical profiler and the RMS method is employed. Subsequently, the study explores the influence of rough tooth surface and contact force fractal parameters on contact stiffness and gear backlash. The results demonstrate the substantial impact of surface topography parameters and contact force on contact stiffness and backlash. Specifically, an increase in the fractal dimension correlates with a reduction in gear backlash and contact stiffness. Conversely, the fractal roughness parameter exhibits the opposite effect. Notably, an increase in contact force enhances contact stiffness.

关键词 ：

fractal theory gear backlash Harmonic drive contact stiffness

引用：

复制并粘贴一种已设定好的引用格式，或利用其中一个链接导入到文献管理软件中。

摘要 ：

Forests are one of the most valuable and necessary resources to protect the ecological balance of the planet, a natural habitat for animals, and they are vital to our lives in many direct and indirect ways. However, forest fires can cause severe damage to the land and many other resources such as property, human life, and wildlife. Previously, metacellular automata have been used to simulate the spread of forest fires, and the traditional metacellular automata model outputs the spread of forest fires by inputting forest fire-related factors such as topography, meteorology, and vegetation type, but these inputs are highly unstable and fires can have an effect on the wind direction and speed, so the inputs must be calibrated. The aim of this study is to explore a forest fire spread simulation model based on Long Short-Term Memory(LSTM) and Cellular Automaton (CA), and to improve the accuracy of the simulation results by calibrating the incoming parameters of the CA in order to improve the fire-fighting action during forest fires. © 2024 IEEE.

关键词 ：

Fire hazards Fires Cellular automata Brain Fire extinguishers Animals Topography Long short-term memory Fireproofing Deforestation

引用：

复制并粘贴一种已设定好的引用格式，或利用其中一个链接导入到文献管理软件中。

摘要 ：

Line laser 3D measurement of gears (LL3DMG) is a critical technology that enables the rapid acquisition of full 3D tooth surface data. This method compensates for the limitations of traditional measurement techniques, which rely on a limited number of points and lines on the tooth surface and involve small sample data processing methods in gear inspection. Instead, it truly reflects the complex 3D topography of the tooth surface, including the size and modification of gears. This article provides a summary and analysis of the main manufacturers of line laser sensors (LLSs), emphasizing their distinct designs and features. It also reveals the prominent role and developmental trends of LLSs in contemporary intelligent manufacturing sectors. Furthermore, based on different application scenarios and equipped devices, a comprehensive analysis and comparison of six different solutions, as well as our team's solution, were conducted. Each solution exhibited unique advantages. This further elaborates on the research status and development trends of LL3DMG-related technologies. This article also introduces the key methodological elements, such as the optical characteristics of the LLSs, pose parameter calibration, measurement pose characteristics, and 3D measurement data preprocessing in LL3DMG, along with possible solutions. Additionally, the challenges associated with LL3DMG are summarized and analyzed, and future research prospects for LL3DMG are analyzed in five main aspects: (1) enhancing and ensuring measurement accuracy, (2) combining intelligence for effective fusion and applications, (3) exploiting and utilizing big data on gear surfaces at depth, (4) facilitating miniaturization and portability of sensors and integration and networking of system, and (5) establishing a gear measurement cloud platform. In summary, these advancements also will present fresh opportunities for the LL3DMG and related fields to develop innovative technologies and products that cater to a wide range of applications.

关键词 ：

Gear Gear measurement Line laser measurement Line laser sensor 3D measurement of gears

引用：

复制并粘贴一种已设定好的引用格式，或利用其中一个链接导入到文献管理软件中。

摘要 ：

Understanding offshore site amplification (AF) characteristics is crucial for marine engineering. Thus far, the spectral ratio (SR) has been widely used to analyze offshore AF characteristics, despite its reliability not yet being fully investigated. In this study, we used 826 ground-motion data recorded at 6 offshore and 19 onshore stations in the Sagami Bay region to reveal the source, path, and AF characteristics using the generalized inversion technique (GIT). The average stress drops for the shallow crustal, subduction interface, and subduction slab earthquakes were 3.55, 6.59, and 7.07 MPa, respectively. The offshore sites were categorized into flat and steep stations based on the local slope gradient (LSG), and systematic AF characteristics were observed. We found that the topography had a negligible influence on the flat free-field station KNG205. AFs obtained using the GIT and SR were analyzed and compared, revealing two main differences: (1) SR-obtained AF values were significantly larger than GIT-obtained AF values above 0.5 Hz and 5 Hz at the flat and steep sites, respectively; (2) resonant frequencies estimated using the SR drifted to lower and higher frequencies for flat and steep sites, respectively. The ineffectiveness of the SR for flat and steep stations was attributed to the effects of topography and seawater pressure on low- and high-frequency vertical ground-motions, respectively. These results suggest that the SR is only reliable for estimating AF curves at marine free-field sites and low-frequency AFs at steep sites. The LSG may play an important role in offshore ground-motion studies.

关键词 ：

Spectral ratio Offshore site response Topographic effect Offshore ground-motion Marine free-field

引用：

复制并粘贴一种已设定好的引用格式，或利用其中一个链接导入到文献管理软件中。

摘要 ：

During the grinding process, K9 optical glass exhibits poor machinability, leading to issues such as crack growth, machining costs, low machining efficiency, and many other problems, seriously restricting its manufacture and application. This paper evaluated the feasibility of picosecond laser-assisted polishing of optical glass workpieces as an economical production method. This study involves a comprehensive exploration of several key aspects, including workpiece dimension control, the surface quality after picosecond laser ablation assessment, the parameters of the picosecond laser equipment optimization, and fine-tuning the parameters of the polishing equipment. The results show that the workpiece surface exhibits a recast layer with an uneven thickness distribution after laser processing, leading to a 38% reduction in luminous flux. Additionally, the roughness of the ablated surface decreases as the pulse repetition rates increase from 40 to 120 kHz. Due to the nonlinear absorption of energy by the amorphous body, the maximum ablation depth occurs around 80 kHz. Furthermore, the unevenly distributed recast layer affects the polishing process. Nevertheless, the efficiency of the picosecond laser-assisted polishing method is greatly improved compared to the conventional method of precision grinding followed by polishing.

关键词 ：

Polishing efficiency Picosecond laser Recast layer K9 optical glass Laser-assisted polishing Topography analysis

引用：

复制并粘贴一种已设定好的引用格式，或利用其中一个链接导入到文献管理软件中。

摘要 ：

River valley terrain can lead to local amplification effects of site seismic responses and significant spatial variation of strong ground motions. This paper presented a semi-analytical solution for the scattering of incident plane P-waves by a saturated river valley with arbitrary shapes containing water, using the moment method and the wave function expansion method. The influence of factors such as valley geometry shapes, soil porosity, wave incident angle and frequency on the seismic response of valley topography is further investigated. Parameter analysis shows that these factors have a significant impact on the site seismic response. Soil porosity has a greater impact on the horizontal response of the site than on the vertical response. Moreover, the soil porosity is directly related to the amplitude of the pore pressure, while the incidence angle and frequency of the incident wave determine the distribution position of the pore pressure amplitude. This semi-analytical solution can be seen as an attempt to solve the scattering problem of incident P wave by saturated river valleys of arbitrary shapes containing water. The purpose of this paper is to provide a reference and a possible way for subsequent scholars to study the analytical solution to this problem. The conclusions drawn from the parameter analysis in this paper can also serve as a theoretical basis for seismic fortification in saturated valley areas.

关键词 ：

Seismic ground motion Amplification effect Seismic wave scattering Moment method River valley Saturated porous medium

引用：

复制并粘贴一种已设定好的引用格式，或利用其中一个链接导入到文献管理软件中。

摘要 ：

Surface defect detection is a common engineering task, and traditional human visual inspection suffers from low efficiency, poor resolution, and a lack of traceable data. We propose a surface-topography detection system based on multicolor latitudinal and longitudinal light sources. By activating multicolor latitudinal and multicolor longitudinal light sources at the same position but at different times, decoupling and highlighting of the surface gradient magnitude and direction in the hue domain of the target surface can be achieved. We used a hot-rolled aluminum sheet as a target and calibrated the vision system, achieving recovery of the gradient magnitude and direction, which provided the necessary conditions for defect data analysis. We also used a hot-rolled aluminum sheet as the target for collecting co-located latitudinal and longitudinal images. In these images, various surface defects were highlighted relative to the background, with good differentiation between the different defects.

关键词 ：

Defect detection Colorimetry Machine vision Surface inspection

引用：

复制并粘贴一种已设定好的引用格式，或利用其中一个链接导入到文献管理软件中。

摘要 ：

Topography can strongly affect ground motion, and studies of the quantification of hill surfaces' topographic effect are relatively rare. In this paper, a new quantitative seismic topographic effect prediction method based upon the BP neural network algorithm and three-dimensional finite element method (FEM) was developed. The FEM simulation results were compared with seismic records and the results show that the PGA and response spectra have a tendency to increase with increasing elevation, but the correlation between PGA amplification factors and slope is not obvious for low hills. New BP neural network models were established for the prediction of amplification factors of PGA and response spectra. Two kinds of input variables' combinations which are convenient to achieve are proposed in this paper for the prediction of amplification factors of PGA and response spectra, respectively. The absolute values of prediction errors can be mostly within 0.1 for PGA amplification factors, and they can be mostly within 0.2 for response spectra's amplification factors. One input variables' combination can achieve better prediction performance while the other one has better expandability of the predictive region. Particularly, the BP models only employ one hidden layer with about a hundred nodes, which makes it efficient for training.

关键词 ：

earthquake disaster prevention BP neural network algorithm finite element method seismic topographic effect

引用：

复制并粘贴一种已设定好的引用格式，或利用其中一个链接导入到文献管理软件中。

摘要 ：

Scanning electron microscope, atomic force microscope and other equipment play an important role in the fields of topography restoration and detection. However, these devices are generally used in nanometer-scale measurement scenarios. For wafer topography quality control scenarios ranging from microns to hundreds of microns, these technologies have problems such as high cost and slow detection speed. Therefore, developing new, low-cost, and high-precision methods is necessary. To address this problem, a wafer surface reconstruction framework is proposed based on the shape-from-focus principle. In view of the characteristics of the large area and micro-small height of the wafer, to solve the limitations of the existing shape from focus framework, which is generally based on a single field, we created a multi-field image sequence rapid acquisition system and proposed the use of pulse control methods to achieve rapid acquisition of large area images. On the other hand, this paper proposes a dual filtering framework combining the Levy flight filtering principle with the SOR algorithm in point cloud filtering to achieve a balance between smoothing the depth map and maintaining the detailed structure, reducing the impact of noise, and improving the morphology restoration accuracy. To avoid splicing seams between fields, the progressive detection multifield stitching technique is used to complete large-area depth data stitching. Experiments were conducted on both synthetic and real objects to verify the effectiveness of the proposed method. In terms of synthesized images, the accuracy of the three methods significantly improved after applying the proposed method framework. After applying the Tenenbaum method framework, its correlation and peak signal-to-noise ratio improved by 7.5% and 38.2%, respectively, and its root mean square error was reduced by 40.7%. The excellent accuracy reconstruction results of the proposed method was verified through accuracy evaluation experiments. The height errors of the three methods used were all higher than 1 mu m. However, after using the proposed method framework, the maximum error was only 0.24 mu m. The experimental results indicated that this method overcomes the area limitation of traditional SFF and is suitable for applying wafer surface morphology measurements.

关键词 ：

defect detection Wafer Levy filtering shape from focus

引用：

复制并粘贴一种已设定好的引用格式，或利用其中一个链接导入到文献管理软件中。