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In-situ Measurements and Thermo-mechanical Simulation of Ti-6Al-4V Laser Solid Forming Processes
摘要： Residual stresses and distortions are two technical obstacles for popularizing the Additive Manufacturing (AM) technology. The evolution of the stresses in AM components during the thermal cycles of the metal depositing process is not yet clear, and more accurate in-situ measurements are necessary to calibrate and validate the numerical tools developed for its simulation. In this work a fully coupled thermo-mechanical analysis to simulate the Laser Solid Forming (LSF) process is carried out. At the same time, an exhaustive experimental campaign is launched to measure the temperature evolution at different locations, as well as the distortions and both the stress and strain fields. The thermal and mechanical responses of single-wall coupons under different process parameters are recorded and compared with the numerical models. Good agreement between the numerical results and the experimental measurements is obtained. Sensitivity analysis demonstrates that the AM process is significantly affected by the laser power and the feeding rate, while poorly influenced by the scanning speed.
关键词： Numerical simulation,Laser Solid Forming (LSF),Thermo-mechanical analysis,Additive manufacturing (AM),In-situ measurements of residual stresses
更新于2025-11-28 14:24:20
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Evaluation of the temperature pattern of a complex body from thermal imaging and 3D information: A method and its MATLAB implementation
摘要： The standard setting of a camera used in Infrared thermography (IRT) is based on the choice of the same values of emissivity and distance for all pixels of a thermal image even if the emissivity depends on the relative position of camera and observed surface. Often this is not a problem. However, the resulting temperature pattern could be inadequate if a body having a complex shape is observed from strongly constrained positions. In order to face this issue, a procedure aimed at providing a correct temperature pattern by using 3D information related to a point cloud is proposed together with its MATLAB implementation (COMAP3 toolbox). For each pixel of a thermal image, the relative position of camera and observed surface is estimated, leading to pixel-specific values of emissivity and distance. The temperature obtained in this way is also mapped onto the point cloud. The effectiveness of the procedure in recognizing areas characterized by peculiar thermal behavior is shown in the case of a historic cylindrical masonry bell tower (Caorle’s bell tower, Venice, Italy).
关键词： Damage recognition,3D thermography,In situ measurements,Thermal imaging,Radiometric JPEG image
更新于2025-09-23 15:23:52
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Regionalization and Dynamic Parameterization of Quantum Yield of Photosynthesis to Improve the Ocean Primary Production Estimates From Remote Sensing
摘要： Quantum yield of photosynthesis (φ) expresses the efficiency of phytoplankton carbon fixation given certain amount of absorbed light. This photophysiological parameter is key to obtaining reliable estimates of primary production (PPsat) in the ocean based on remote sensing information. Several works have shown that φ changes temporally, vertically, and horizontally in the ocean. One of the primary factors ruling its variability is light intensity and thereby, it can be modeled as a function of Photosynthetically Available Radiation (PAR). We estimated φ utilizing long time-series collected in the North Subtropical Oligotrophic Gyres, at HOT and BATS stations (Pacific and Atlantic oceans, respectively). Subsequently the maximum quantum yield (φm) and Kφ (PAR value at half φm) were calculated. Median φm values were ～0.040 and 0.063 mol C mol photons?1 at HOT and BATS, respectively, with higher values in winter. Kφ values were ～8.0 and 10.8 mol photons m?2 d?1 for HOT and BATS, respectively. Seasonal variability in Kφ showed its peak in summer. Dynamical parameterizations for both regions are indicated by their temporal behaviors, where φm is related to temperature at BATS while Kφ to PAR, in both stations. At HOT, φm was weakly related to temperature and its median annual value was used for the whole data series. Differences in the study areas, even though both belong to Subtropical Gyres, reinforced the demand for regional parameterizations in PPsat models. Such parameterizations were finally included in a PPsat model based on phytoplankton absorption (PPsat?aphy?based), where results showed that the PPsat?aphy?based model coupled with dynamical parameterization improved PPsat estimates. Compared with PPsat estimates from the widely used VGPM, a model based on chlorophyll concentration (PPsat?chl?based), PPsat?aphy?based reduced model-measurement differences from ～62.8 to ～8.3% at HOT, along with well-matched seasonal cycle of PP (R2 = 0.76). There is not significant reduction in model-measurement differences between PPsat?chl?based and PPsat?aphy?based PP at BATS though (37.8 vs. 36.4%), but much better agreement in seasonal cycles with PPsat?aphy?based (R2 increased from 0.34 to 0.71). Our results point to improved estimation of PPsat by parameterized quantum yield along with phytoplankton absorption coefficient at the core.
关键词： quantum yield of photosynthesis,ocean color,phytoplankton primary production,in situ measurements,dynamical parameterization,marine seasonal variability
更新于2025-09-23 15:21:01
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Recent Progress in Quantitative Land Remote Sensing in China
摘要： During the past forty years, since the first book with a title mentioning quantitative and remote sensing was published [1], quantitative land remote sensing has advanced dramatically, and numerous books have been published since then [2–6] although some of them did not use quantitative land remote sensing in their titles. Quantitative land remote sensing has not been explicitly defined in the literature, but we consider it as a sub-discipline of remote sensing including the following components (see Figure 1): radiometric preprocessing, inversion, high-level product generation, and applications. Many inversion algorithms rely on physical models of radiation regimes of landscapes, which link with remotely-sensed data. Generating high-level satellite products of land surface biophysical and biochemical variables create the key bridge between remote sensing science and applications. Conducting in situ measurements for validation of inversion algorithms and satellite products is also a critical component. Application of satellite products to address scientific and societal relevant issues will ultimately decide the future of quantitative land remote sensing.
关键词： inversion algorithms,in situ measurements,land surface biophysical and biochemical variables,satellite data,quantitative land remote sensing
更新于2025-09-23 15:21:01
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Mobile Monitoring—Open-Source Based Optical Sensor System for Service-Oriented Turbidity and Dissolved Organic Matter Monitoring
摘要： The protection and sustainable use of aquatic resources require a better understanding of fresh water sources, limnic ecosystems, and oceans. The effects of global change, intensive use of natural resources and the complex interactions between humans and the environment show different effects at different scales. Current research approaches are not sufficient to appropriately take account of the heterogeneity and dynamics of aquatic ecosystems. A major challenge in applied environmental research is to extend methods for holistic monitoring and long-term observation technologies with enhanced resolution over both space and time. In this study, turbidity and the content of dissolved organic matter (DOM) are key parameters, as they are of importance for assessing the health of aquatic ecosystems and the state of ecosystem services (e.g., the provision of drinking water). Photonics and optical sensors as well as integrated circuits and open-source based components open interesting possibilities to overcome the current lack of adaptive and service-oriented sensor systems. An open source based optical sensor system was developed, which enables a user-specific, modular and adaptive in-situ monitoring of the turbidity and the dissolved organic substance content almost in real time. Quantification is based on attenuation or transmission measurements with two narrowband LEDs and corresponding detectors in the ultraviolet (DOM content) and infrared range (turbidity) of the electromagnetic spectrum. The developed in-situ sensor system shows a very high agreement with the results obtained using a laboratory photometer but with less methodological effort. First tests carried out in the area close to the city of Leipzig (Saxony, Germany) show promising results. The in-situ sensor system is able to acquire the optical attenuation with a sampling rate up to 0.1 Hz. Due to the fact that data is visualized directly with the help of web services, even the quality of data collection can be improved by assisting the selection of sampling points or a direct spatio-temporal data feedback. What this approach illustrates is the fact that open-source technologies and microelectronics can now be used to implement resilient and promising sensor systems that can set new standards in terms of performance and usability within applied environmental research.
关键词： internet of things,assisted monitoring,attenuation sensor,water quality,photonics sensing,in-situ measurements
更新于2025-09-16 10:30:52
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Open-source sensor for measuring oxygen partial pressures below 100 microbars
摘要： The ability to measure partial pressures of oxygen below 100 microbars and nanomolar dissolved oxygen concentrations in in situ laboratory systems benefits many fields including microbiology, geobiology, oceanography, chemistry, and materials science. Here, we present an easily constructible open-source design for a networked luminescence lifetime measurement system for in situ measurements in arbitrary laboratory containers. The system is well suited for measuring oxygen partial pressures in the 0–100 μbar range, with the maximum potentially usable upper range limit at around 10 mbar, depending on experimental conditions. The sensor has a limited drift and its detectability limit for oxygen is at 0.02 μbar for short timescale measurements. Each sensor can connect to a Wi-Fi network and send the logged data either over the Internet or to a local server, enabling a large number of parallel unattended experiments. Designs are also provided for attaching the sensor to various commercially available containers used in laboratories. The design files are released under an open source license, which enables other laboratories to build, customize, and use these sensors.
关键词： in situ measurements,luminescence lifetime,oxygen sensor,trace oxygen,open-source
更新于2025-09-09 09:28:46