The estimation of caloric content of vegetation is relevant in areas such as biofuels and forest fire prevention. In this work we explore the transmission mechanism of infrared radiation through a leaf by finite element analysis to determine the energy transmission and reflection. We quantify the absorption inside the leaf using a wavelength at 1064 nm. The results obtained are determined experimentally at incidence normal to the leaf surface. We use an infrared laser source, controlling its power settings and a neutral density filter for step-wise power increments. We assumed a non-porous, uniform material, a constant refractive index. We select a specific absorption coefficient according to the senescent state of the leaf. The results describe the relationship between the absorption measured experimentally and computed by finite element analysis (FEA).
3D printing technologies have allowed the development of prototypes in several fields, such as clinical, aerospace, and infrastructure, to name a few. Another use is to adapt the laboratory instruments to customized applications to improve experiments and measurements in the data acquisition process. Some equipment is modified to include low-cost cameras, optical components, sensors, and mechanical artifacts using printed accessories employing PLA or PETG filaments, such as telescopes, microscopes, and spectrometers. These accessories allow us to maximize the features of the instruments and reduce the research cost. We describe a semi-automatic method for microalgae counting based on a digital microscope adapted to a 3D printing mechanical support and image processing in Matlab. Calibration will be carried out using a Neubauer chamber but will not be required for measurements, which makes a difference compared to similar methods. The results obtained for micro-algae counting show an average error of less than 5% compared to visual counting conducted by a biochemical specialist. We are describe a simple and low-cost method of counting microalgae using 3D printing technologies.
A laser shock wave is a pressure wave that travels through a material at supersonic speed induced by a high-power laser pulse. Shock waves suddenly change direction as reflected at the physical limits of the medium, producing interference between the wave remnants. The reflected wave reaches the front surface transiting a distance as a function of the thickness and the reflection angle. The time it takes for the shock wave from being induced to reflect toward the front surface of the material can be used to determine the thickness of the propagation medium. A finite element method estimate the propagation of a laser shock wave in four basic geometric shapes of 6061-T6 aluminum alloy. The time it takes to reach the front surface of the geometric shapes is measured. Its controlled the material thickness and spatial coordinate of the induction. The effects of the porosity, absorption and transmission of the medium are ignored. The results demonstrate the feasibility of use the time-of flight as a thickness measurement and a distribution of compression and pressure zones inside the medium generated by the wave interference. Some applications of this method are to determine the thickness of solid materials, the estimation of caverns or aquifers on geophysics, and the determination of the density of a material.
Remote sensing used in vegetation monitoring has been a significant study area for decades. With the advent of multispectral and hyperspectral cameras, detecting healthy vegetation in forests and crops were more accessible through the ratio of different spectral bands that resulted in other vegetation indices. However, even with the usefulness and practicality of these methods, they need to be more accurate since they are relative values that depend on several factors of the internal composition of the vegetation. This work proposes the analysis of a spectral bandwidth of a central wavelength of 1 μm, using a conventional CCD camera as a detector with a bandpass filter with a linewidth of 10 nm. This range presents characteristics of water absorption but also reflectance due to the cellulose of the cell walls of the leaves. In this way, using the electro-optical array, the radiation reflected changes by several leaves will be analyzed considering the hydration and deterioration of the leaf.
The moisture content of forest fuel on the forest floor is a determining factor in assessing the ignition and spread of fire. The measurement of moisture content through indirect methods benefits obtaining and visualizing results immediately. Some indirect methods are based on the measurement of environmental variables, but they require calibration for specific tree data. In this work, we examine the diffuse reflectance spectra of the leaves of different tree species in two spectral bands, obtaining a relationship with the measurement of the moisture content of the leaves through the indirect method based on meteorological factors. This relationship contributes to the characterization of remote sensing devices implemented in measuring moisture content in biomass dry on the forest floor, improving measurement accuracy.
Study of vegetation by non-invasive methods is a relevant topic for the preservation of the forests, by mean the biochemical analysis of vegetation, the study of the plants and analysis of their behavior with external agents. These methods are based on the spectral signatures of leaves under different behavior conditions. This information can be used in remote sensing techniques for various application through the use of multispectral images or measurements of spectroradiometers. In this document, we examine the diffuse reflectance spectra of the leaves of tree species in two spectral ranges. The first region is enclosed from 0.4 μm to 2.5 μm which corresponds to the solar radiation. The second region covers from 2.5 μm to 20 μm. The study explains the change in the specific signatures of the leaves in relation to the internal decomposition of the foliar plate, due to dehydration of the leaf, the loss of chlorophyll, the production of anthocyanin, and the destruction of the cellular structure, considering two senescent states.
La Primavera forest is the main climate regulator in the metropolitan area of Guadalajara, the second most populated megalopolis in Mexico with approximately 4.4 million people. This forest area has been a focus of fires in the last decade and it is deteriorating the quality of life of the inhabitants. Leaves from the endemic forest provide information about their biochemical composition and physiology. This information is enclosed in the spectral range of the visible band to the middle infrared (400 nm at 2500 nm). In this paper we examine the reflectance of six endemic species leaves of La Primavera forest, considering the measurement in fresh and dry samples. Measurements will be obtained with a Vis-NIR spectrometer that uses a calibrated light source. A formal collection of the optical properties of tree leaves in La Primavera forest does not exist, but it is important to classify about the type of vegetation in the area. In addition, it will provide information to generate vegetation inventories, provide data to the forest fire prevention systems, pest control and erosion in the area.
Fuel Moisture Content (FMC) and leaf biochemical compounds are parameters used to determine forest ignition and can be obtained by the use of different methods, included optical and chemical techniques. Chemical techniques require approximately 20 hours to determine forest fuel chemical compounds and FMC. In contrast, optical techniques need a few minutes to know the FMC. However, with this is not possible to determine the chemical compounds without a previous treatment. PROSPECT is a radiative transfer model technique to describe reflectance and transmittance of leaves. Using visual and near infrared (Vis-NIR) spectroscopy, the specific absorption coefficient of leaf extract is obtained. This is used as a parameter for invert PROSPECT model and quantify resins, oils and waxes which constitute forest fuel. This research will give the basis for remote Vis-NIR spectroscopy using unmanned aerial vehicles (UAVs) for a dynamical ignition parameters acquisition.
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