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1
artículo
Publicado 2018
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Attenuation imaging using spectral techniques such as the spectral log difference (SLD) method suffers from a severe trade-off between spatial resolution and estimation variance. Recently, the regularized spectral log difference (RSLD) method was proposed as a technique that extends such trade-off by incorporating spatial priors (i.e., total variation) in the inversion process. However, the reduction of the variance of attenuation images could also be accomplished by post-processing of the attenuation maps using noise reduction techniques. The main goal of this study is to determine which strategy (i.e., noise handling during or after the attenuation image reconstruction) provides attenuation maps of better quality, both with synthetic data and experimental data obtained from calibrated physical phantoms. The results suggest that the noise rejection mechanism of RSLD significantly outper...
2
tesis de maestría
Publicado 2017
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The attenuation coefficient slope (ACS) has the potential to be used for tissue characterization and as a diagnostic ultrasound tool, hence complementing B-mode images. The ACS can be valuable for estimation of other ultrasound parameters such as the backscatter coefficient. There is a well-known tradeoff between the precision of the estimated ACS values and the data block size used in spectral-based techniques such as the spectral log difference (SLD). This trade-off limits the practical usefulness of spectral-based attenuation imaging techniques. In this thesis work, the regularized spectral log difference (RSLD) technique is presented in detail and evaluated with simulations and experiments with physical phantoms, ex vivo and in vivo. The ACS values obtained when using the RSLD technique were compared to the ones obtained when using the SLD technique, as well as the ground truth ACS v...
3
tesis de maestría
Publicado 2017
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The attenuation coefficient slope (ACS) has the potential to be used for tissue characterization and as a diagnostic ultrasound tool, hence complementing B-mode images. The ACS can be valuable for estimation of other ultrasound parameters such as the backscatter coefficient. There is a well-known tradeoff between the precision of the estimated ACS values and the data block size used in spectral-based techniques such as the spectral log difference (SLD). This trade-off limits the practical usefulness of spectral-based attenuation imaging techniques. In this thesis work, the regularized spectral log difference (RSLD) technique is presented in detail and evaluated with simulations and experiments with physical phantoms, ex vivo and in vivo. The ACS values obtained when using the RSLD technique were compared to the ones obtained when using the SLD technique, as well as the ground truth ACS v...
4
tesis de maestría
Publicado 2017
Enlace
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The attenuation coefficient slope (ACS) has the potential to be used for tissue characterization and as a diagnostic ultrasound tool, hence complementing B-mode images. The ACS can be valuable for estimation of other ultrasound parameters such as the backscatter coefficient. There is a well-known tradeoff between the precision of the estimated ACS values and the data block size used in spectral-based techniques such as the spectral log difference (SLD). This trade-off limits the practical usefulness of spectral-based attenuation imaging techniques. In this thesis work, the regularized spectral log difference (RSLD) technique is presented in detail and evaluated with simulations and experiments with physical phantoms, ex vivo and in vivo. The ACS values obtained when using the RSLD technique were compared to the ones obtained when using the SLD technique, as well as the ground truth ACS v...
5
artículo
Publicado 2025
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Tarwi (Lupinus mutabilis S.) is a legume native to the Andes, recognized for its high nutritional value, which gives it great potential in food security programs. Therefore, understanding and advancing the conservation of its morphological diversity is essential. In this study, 140 accessions from the national germplasm collection of the National Institute of Agrarian Innovation of Peru were evaluated, along with two cultivars ("INIA 445 Masacanchino" and "Andenes 90"). A traditional agro-morphological characterization was conducted using 16 quantitative and 40 qualitative descriptors, complemented by phenological data obtained from time series of reflectance indices generated by Unmanned Aerial Vehicles (UAVs). Additionally, a principal component analysis (PCA) was applied to select the most relevant variables, and a clustering analysis along with a dendrogram was developed to classify ...
6
artículo
Publicado 2025
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Tarwi (Lupinus mutabilis S.) is a legume native to the Andes, recognized for its high nutritional value, which gives it great potential in food security programs. Therefore, understanding and advancing the conservation of its morphological diversity is essential. In this study, 140 accessions from the national germplasm collection of the National Institute of Agrarian Innovation of Peru were evaluated, along with two cultivars ("INIA 445 Masacanchino" and "Andenes 90"). A traditional agro-morphological characterization was conducted using 16 quantitative and 40 qualitative descriptors, complemented by phenological data obtained from time series of reflectance indices generated by Unmanned Aerial Vehicles (UAVs). Additionally, a principal component analysis (PCA) was applied to select the most relevant variables, and a clustering analysis along with a dendrogram was developed to classify ...
7
tesis doctoral
Publicado 2023
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Accurate produced PV energy estimation is critical to business decisions under long-term investments in PV on a utility scale. PV energy yield is affected by different sites' specific conditions. The variability of the spectral distribution after temperature and irradiation is a site condition that impacts energy yield estimates. Evaluating the impact of the spectral irradiance distribution on the PV performance generally requires accurate information about the PV device's spectral response and the site’s measured spectra. Detailed spectral and device information may not always be available. This study analyzes the interrelations between device-dependent and device-independent energetic spectral indicators with spectral data from nine sites with different climates and latitudes, aiming to relax the requirement for detailed device and spectral information. First, an apparent correlation...
8
tesis doctoral
Publicado 2023
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Accurate produced PV energy estimation is critical to business decisions under long-term investments in PV on a utility scale. PV energy yield is affected by different sites' specific conditions. The variability of the spectral distribution after temperature and irradiation is a site condition that impacts energy yield estimates. Evaluating the impact of the spectral irradiance distribution on the PV performance generally requires accurate information about the PV device's spectral response and the site’s measured spectra. Detailed spectral and device information may not always be available. This study analyzes the interrelations between device-dependent and device-independent energetic spectral indicators with spectral data from nine sites with different climates and latitudes, aiming to relax the requirement for detailed device and spectral information. First, an apparent correlation...
9
artículo
Publicado 2025
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Biochar, a carbon-rich material produced through oxygen-limited pyrolysis of organic biomass, demonstrates exceptional potential as a soil amendment due to its porous structure and stability. This research investigated the impact of guinea pig manure biochar on three vegetable species cultivated in high Andean conditions: spinach (Spinacia oleracea L.), cabbage (Brassica oleracea var.), and chard (Beta vulgaris var.). The study implemented four biochar application rates (0, 10, 20, and 30 t/ha) and measured comprehensive agronomic parameters including leaf count, leaf length, and fresh/dry biomass of both leaves and roots. Simultaneously, UAV-captured multispectral imagery provided spectral indices that were integrated with agronomic data into machine learning models: linear regression, support vector machines (SVM), and regression trees (CART). Results demonstrated significant vegetativ...
10
tesis de grado
Publicado 2025
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Forest fires are one of the main problems that affect biodiversity and forest heterogeneity, which are caused by human or natural activities and even driven by climate change. The objective of this study was to analyze the severity of forest fires with the NBR index (Normalized Burn Ratio) in highland areas of Peru, and evaluate the vegetative recovery of forest species in the affected area with the NDVI index (Normalized Difference Vegetation Index). As a result, it was obtained that the type of vegetation in the affected area is the Andean Pajonal, the level of severity in the study area ranges from low to moderately high, with low severity being the predominant one, which occupies 57,562% of the study area. The NDVI evaluation of 2 weeks before, 2 weeks after and 3 months after the event show that there is a vegetative regeneration of the vegetation cover, two weeks after the event in...
11
artículo
Publicado 2022
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Climate change, as well as the appearance of pests and diseases, are affecting olive plantations (Olea europaea L.) and the production of olives in the world, therefore, there is an urgent need for tools to help us identify the spatial and temporal evolution of the olive groves, regarding the attack of pests, in this case, the Orthezia olivicola and the olive borer Phloeotribus scarabaeoides. In this work, we use information from freely available satellite images that allowed us to carry out spatial and temporal analysis and the combination of vegetation indices. For the studied area, according to the values of the NDVI (Normalized Difference Vegetation Index), it was identified that the surface of diseased plants ranges from 42% to 68%, moderately healthy plants from 2% to 18%, and the state of the plantation considered as very healthy plants with a tendency to zero, which means that pr...
12
objeto de conferencia
Publicado 2024
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This article presents the results of the analysis of predominant soil periods using the spectral ratio (HVSR) methodology, based on strong motion records at seismic stations in the Chorrillos district, Lima, Peru, a high seismicity area at the western edge of South America. The district contains fine soil deposits, different to the coarse alluvial conglomerate of Lima downtown. The seismic stations are located on sandy soils interspersed with clay strata, moderately compact to dense aeolian sands of variable thickness, and silty-clay soils followed by peat with intercalations of silty sand, according to the existing seismic microzonation. The results indicate that the HVSR method can be very useful to determine the predominant soil periods, which represent the soil profile on which the strong motion record has been recorded. These soil periods, which are in the range of 0.21 s to 0.49 s,...
13
artículo
Publicado 2017
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El primer sensor con observación multibanda en la región infrarroja térmica (8-12 micrómetros) con 90 metros de resolución espacial y 5 bandas espectrales especialmente diseñadas para discriminar rocas de la corteza terrestre. Se aplicaron diferentes procedimientos para discriminar minerales de alteración y grupos de roca utilizando no sólo la banda infrarroja térmica sino también las bandas visible e infrarroja cercana.El área de estudio se encuentra ubicada en el Departamento de Cuzco en la porción sur del Cinturón Volcánico Terciario del Perú y ubicada a 170 kilómetros al noroeste de Arequipa. La zona se encuentra dentro del altiplano peruano a una altitud de 4.470 a 5.370 metros. La disponibilidad de datos multiespectrales a partir del satélite ASTER (radar espacial de reflexión radiométrica) ha proporcionado y aumentado el potencial para la cartografía de los sis...
14
artículo
Publicado 2017
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Advance spaceborne thermal emission and reflection radiometer (aster) is the first sensor with multi band observation in thermal infrared region (8-12 micrometers) with 90 meters of spatial resolution and 5 spectral bands specially designed to discriminate rocks from earth crust. Different process were applied in order to discriminate alteration minerals and rock groups by using not only the thermal infrared band but also the visible and near infrared bands.The area of study is located is situated in the Department of Cuzco in the southern portion of the Peru Tertiary Volcanic Belt and located 170 kilometres northwest of Arequipa. The area lies within the Peruvian altiplano at an altitude of 4,470 to 5,370 metres. The availability of multispectral data from the satellite- borne ASTER (advance Spaceborne Thermal emission Reflection Radiometer) instrument has provided and increased potenti...
15
artículo
Publicado 2019
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The effective temperature for a sample of 62 solar-type stars has been determined fitting theoretical spectral profiles to observed Hα lines (6562.8 A). The stars analyzed has been observed using the 2.7 m Harlan J. Smith telescope at the McDonald Observatory of the University of Texas. The theoretical profiles are based on recent models of stellar atmospheres and quantum theory. The calculated temperatures have internal errors of ≈ 20 K with other techniques and speculate about the origin of the observed differences.
16
tesis de maestría
Publicado 2019
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I would like to thank the National Council of Science, Technology and Technological Innovation (Concytec) from Peru for the award of a scholarship which made it possible to do this research work.
17
tesis de maestría
Publicado 2019
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Semiconductor-insulator interfaces play an important role in the performance of many different electronic and optoelectronic devices such as transistors, LEDs, lasers and solar cells. Particularly, the recombination of photo-generated charge carriers at interfaces in crystalline silicon solar cells causes a dramatic efficiency reduction. Therefore, during the fabrication process, the crystalline silicon must be subjected to prior superficial passivation; typically through an insulating layer such as SiO2, SiNx or AlOx. The function of this passivating layer is to reduce electrical recombination losses in interfacial defect states originating from dangling bonds. The associated passivation parameters are, on the one hand, stable charges within the insulating layer (Qox) that by repelling a certain type of charge carrier from the crystalline silicon surface, reduces its recombination effec...
18
tesis de maestría
Publicado 2019
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Semiconductor-insulator interfaces play an important role in the performance of many different electronic and optoelectronic devices such as transistors, LEDs, lasers and solar cells. Particularly, the recombination of photo-generated charge carriers at interfaces in crystalline silicon solar cells causes a dramatic efficiency reduction. Therefore, during the fabrication process, the crystalline silicon must be subjected to prior superficial passivation; typically through an insulating layer such as SiO2, SiNx or AlOx. The function of this passivating layer is to reduce electrical recombination losses in interfacial defect states originating from dangling bonds. The associated passivation parameters are, on the one hand, stable charges within the insulating layer (Qox) that by repelling a certain type of charge carrier from the crystalline silicon surface, reduces its recombination effec...
19
tesis de maestría
Publicado 2018
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The skin is the largest organ of the body that protects it from the external environment. High- frequency ultra sound (HF-US) has been used to visualize the skin in depth and to diagnose some pathologies in dermatological applications. Quantitative ultrasound (QUS) includes several techniques that provide values of particular physical properties. In this thesis work, three QUS parameters are explained and used to characterize healthy skin through HF-US: attenuation coefficient slope (ACS), backscatter coefficient (BSC) and shear wave speed (SWS). They were estimated with the regularized spectral-log difference (RSLD) method, the reference phan- tom method, and the crawling wave sonoelastography method, respectively. All the three parameters were assessed in phantoms, ex vivo and in vivo skin. In calibrated phantoms, RSLD showed a reduc- tion of up to 93% of the standard deviation concern...
20
artículo
Publicado 2024
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There are some documents that deal with the use of spectral analysis of AM modulation but a joint analysis in the time and frequency domain is not found. This is why the aim of the present study was to show the benefits of using state-of-the-art oscilloscopes and spectrum analyzers for teaching carrier-present AM modulation (DSB-FC) in the time and frequency domains. For this, a spectrum analyzer, a radio frequency generator and an oscilloscope were used and we worked with different frequencies and modulation percentages. With the oscilloscope, the effective voltage (VRMS) and the peak-to-peak voltage of the pure carrier (Vcpp) and for the modulated carrier were measured, from these data the carrier power Pc and the total power PT were calculated, then the values. With the spectrum analyzer, the carrier power, total power (channel power) and the powers of the lower and upper sidebands we...
