209 research outputs found
A novel diffusion tensor imaging-based computer-aided diagnostic system for early diagnosis of autism.
Autism spectrum disorders (ASDs) denote a significant growing public health concern. Currently, one in 68 children has been diagnosed with ASDs in the United States, and most children are diagnosed after the age of four, despite the fact that ASDs can be identified as early as age two. The ultimate goal of this thesis is to develop a computer-aided diagnosis (CAD) system for the accurate and early diagnosis of ASDs using diffusion tensor imaging (DTI). This CAD system consists of three main steps. First, the brain tissues are segmented based on three image descriptors: a visual appearance model that has the ability to model a large dimensional feature space, a shape model that is adapted during the segmentation process using first- and second-order visual appearance features, and a spatially invariant second-order homogeneity descriptor. Secondly, discriminatory features are extracted from the segmented brains. Cortex shape variability is assessed using shape construction methods, and white matter integrity is further examined through connectivity analysis. Finally, the diagnostic capabilities of these extracted features are investigated. The accuracy of the presented CAD system has been tested on 25 infants with a high risk of developing ASDs. The preliminary diagnostic results are promising in identifying autistic from control patients
Use of ultrasound for the characterization and correction of textural defects in dry-cured ham
Tesis por compendio[EN] Dry-cured ham is a product highly appreciated by consumers, nevertheless, there are a
large number of manufacturing process-related parameters, as well as ham intrinsic factors, that
compromise its final quality. One of the main problems in the quality of dry-cured ham is the
appearance of textural defects, in particular, the development of pastiness. This defect is
characterized by an excessive softness and loss of elastic behavior of the ham and when tasted, it
provokes a feeling similar to the mouth-coating sensation produced by a flour-water paste during
the mastication process. Pastiness also makes slicing difficult and promotes the adhesiveness
between slices. Currently, the methods available to measure ham pastiness are time-consuming
and destructive. For this reason, the seek of faster and non-destructive technologies capable of
detecting pastiness is of great importance. In this sense, different technologies such as near
infrared spectroscopy, X-rays or ultrasound, that have been previously tested for the nondestructive characterization of different meat products, could be of interest for the detection of
ham pastiness.
Different approaches, such as the use of high hydrostatic pressure (HHP) or the
application of low-temperature long-time thermal treatments (LTLT) at the end of the ham
manufacturing, have been previously addressed for the correction of pastiness in dry-cured ham.
Notwithstanding, the high cost and the long time required for the HHP and LTLT treatments,
respectively, highlights the need for moderate cost and faster alternatives.
In this context, the main goals of this thesis were to determine the feasibility of using low
intensity ultrasound to non-destructively detect the appearance of pastiness during ham
manufacturing and to characterize the level of pastiness in the final product, as well as to explore
the feasibility of mild ultrasonic assisted thermal treatments to correct this textural defect.
To meet the goal of ham pastiness characterization and correction, a customized drycured ham manufacturing was designed and carried out in order to obtain hams with different
levels of pastiness with no remarkable differences on the salt content. During ham manufacturing,
the feasibility of using contact ultrasound to monitor the appearance of pastiness was addressed.
The ultrasonic velocity was measured in the raw ham, at the end of the salting and post-salting
stages, 3 times during the drying-maturation and once the manufacturing was finished. At the end
of the manufacturing, the pastiness level (high, medium and no pasty) was also sensory evaluated
by an expert panel. As the manufacturing progressed, a progressive increase in the ultrasonic
velocity, from 1536 m/s in the raw ham to 1713 m/s in the final dry-cured ham, was found.
Notwithstanding, the increase in the ultrasonic velocity was not related with the pastiness defect,
probably because the ham texture changes linked to pastiness were masked by the great influence
of the compositional changes (salt gain and moisture loss) on the ultrasonic velocity. Therefore,
the ultrasonic velocity was not an effective parameter to detect the appearance of pastiness in
hams during manufacturing, neither to classify them according to its pastiness level at the end of
the manufacturing.
Contact ultrasound was also used to monitor the compositional and textural changes
taking place along the ham post-salting stage. For this purpose, another batch of hams was salted
and post-salting times from 7 to 56 days were tested. During post-salting, the hams were weighted
and the ultrasonic velocity was measured every 2 days. Each 7 post-salting days, the composition
and the textural properties of a different ham were destructively analyzed. The ham weight loss
during the post-salting stage was satisfactorily (r=0.95) described by the increase in the ultrasonic
velocity. Moreover, the salt distribution and the moisture loss in the internal parts of the ham were
satisfactorily related (r=0.93 and r=0.86, respectively) with the increase in the ultrasonic velocity.
The variation in the ham hardness during post-salting was negligible and hence, the velocity
increase was mainly attributed to the compositional changes, being barely affected by the changes
in texture.
The hams obtained after the customized manufacturing were sliced and the ultrasonic
velocity and attenuation were measured on the Biceps femoris muscle with the aim of nondestructively finding out its pastiness level. Furthermore, in order to better analyze this textural
defect, the composition, protein degradation, instrumental texture and microstructure of the hams
were analyzed. Pasty samples presented the highest proteolysis index (38.7% compared to 33.1%
for non-pasty hams), exhibited the more relevant structural degradation (merged myofibril
structures and appearance of large gaps) and consequently, were the softest (5.4 N of hardness
compared to 16.7 N for non-pasty hams) and presented the most intense viscous behavior (0.434
compared to 0.372 for non-pasty hams), although a high degree of experimental variability was
found. The non-destructive assessment performed with ultrasound revealed that ultrasonic
attenuation could be successfully applied for the grading of dry-cured ham slices according to its
pastiness level. Thus, the greater the pastiness, the higher the ultrasonic attenuation, being the
average attenuation coefficient for high, medium and no-pasty samples 48.2, 45.4 and 43.1 Np/m,
respectively. Notwithstanding, the ultrasonic velocity was similar in all the ham samples,
regardless its pastiness level. As observed in whole hams, the ultrasonic velocity was not a
satisfactory parameter to detect pastiness in sliced ham, since the large influence of the
composition on the ultrasonic velocity added to a similar salt and moisture content of the samples,
regardless its pastiness level, led to a similar velocity for the different pastiness levels.
Air-coupled ultrasonic techniques in both through-transmission and pulse-echo modes
were developed for the characterization of dry-cured ham texture. The non-invasive nature of aircoupled ultrasound allows a contactless measurement, which makes easier its industrial
implementation compared to conventional ultrasound techniques for high speed applications
without material surface alteration and cross-contamination between food items.
As for corrective actions of the texture defects in dry-cured ham, mild thermal treatments
in two different heating media (water and air) were evaluated. Furthermore, the feasibility of
intensifying these mild thermal treatments with the assistance of power ultrasound was
considered. For that purpose, commercial vacuum-packed dry-cured ham slices were heated in a
liquid medium, with and without ultrasonic assistance, at different temperatures (40, 45 and 50
ºC), measuring the temperature in the Biceps femoris and in the Semimembranosus muscles.
Regarding the treatments in air, commercial vacuum-packed dry-cured ham cylinders were used.
In the first set of experiments, ham was heated at a constant air velocity (2 m/s) until different
temperatures (40, 45 and 50 ºC) were reached. While in the second set of experiments, ham was
treated at constant air temperature (50 ºC) at different air velocities (1, 2, 3, 4 and 6 m/s). In both
sets, the treatments were performed with and without power ultrasound application, measuring
the temperature in the center of the cylinder. Thermal treatments were extended until a target
temperature of 5 ºC lower than the medium (water-air) heating temperature was reached, thus,
holding temperature stage did not exist and the treatments only considered the heating one. The
heating kinetics of the ham treated in both water and air heating media were mathematically
described by means of a heat conduction model. Once the heating finalized, the textural changes
of ham (hardness and elastic behavior) were evaluated. The experiments showed that power
ultrasound application sped up the heat transfer, significantly (p<0.05) shortening the heating time
and increasing the apparent thermal diffusivity up to 51 and 37% for water and air heat treatments,
respectively. For the thermal treatments using water, the increase in temperature during the
heating brought about a lower ultrasonic intensification (the apparent thermal diffusivity was
increased by 51% at 40 ºC compared to the 21% at 50 ºC). On the contrary, in experiments with
air, the higher the temperature, the greater the ultrasonic enhancement (the apparent thermal
diffusivity was increased by 5% at 40 ºC compared to the 38% at 50 ºC). The effect of the
ultrasound application decreased as the air velocity increased, being minimal when the air velocity
was the highest (the apparent thermal diffusivity was increased by 21% at 1 m/s compared to the
5% at 6 m/s). As regards the changes in the textural properties of ham after the mild thermal
treatments at short times, an increase in hardness and elastic behavior was observed.
Finally, the texture correction in dry-cured ham with different levels of pastiness was
tackled. For this purpose, vacuum-packed dry-cured ham slices with high, medium and no
pastiness were heated in a liquid medium at 40 and 50 ºC for a longer time (5 h, including heating and holding stages) than heating experiments, with and without the assistance of power ultrasound
during the heating phase. The texture (hardness, elastic behavior and adhesiveness) and the
microstructure of the ham was evaluated in both treated and control samples. After the mild
thermal treatments, the texture of ham was improved since the hardness was increased (102%)
and the viscous behavior diminished (11%). On average, the increase of hardness at 50 ºC was
159% higher than at 40 ºC, while the decrease of the viscous behavior was 13.5% larger at 50 ºC
compared to 40 ºC. The ham adhesiveness was also enhanced independently of the treatment
temperature, with a 55% reduction being observed. The application of power ultrasound during
the heating phase did not involve any additional textural change. Likewise, after the thermal
treatments, the microstructure of hams with pastiness notably changed, experiencing a severe
shrinkage of the myofibrils, which contributed to explain the reported textural changes.
In conclusion, pastiness is a relevant and highly complex textural defect in dry-cured ham.
The use of contact ultrasound and the measurement of the ultrasonic attenuation could be
considered a potential technology to non-destructively detect and characterize pastiness in sliced
dry-cured ham. Future work should focus on extending this approach to identify pasty whole
hams, considering for this purpose the use of air-coupled ultrasound. Moreover, the use of mild
thermal treatments in liquid or gas media could be a feasible method to correct the defective
texture of dry-cured hams and the application of power ultrasound during the heating phase could
be a relevant means of speeding up the thermal treatments.[ES] El jamón curado es un producto muy apreciado por los consumidores, sin embargo,
existen numerosos parámetros relacionados con el procesado, asà como factores intrÃnsecos del
jamón, que comprometen su calidad final. Uno de los principales problemas de calidad del jamón
curado es la aparición de defectos de textura, concretamente, el desarrollo de pastosidad. Este
defecto se caracteriza por una textura excesivamente blanda y un comportamiento menos elástico
del jamón. A nivel sensorial, provoca una sensación de recubrimiento en boca similar a la
masticación de una pasta de harina y agua. La pastosidad también dificulta el loncheado y
promueve la adhesividad entre lonchas. Actualmente, los métodos disponibles para caracterizar
la pastosidad requieren mucho tiempo y son destructivos. Por esta razón, la búsqueda de
tecnologÃas más rápidas y no destructivas capaces de detectar la pastosidad es de gran
importancia. En este sentido, distintas tecnologÃas como espectroscopÃa de infrarrojo cercano,
rayos-X o ultrasonidos, que han sido ensayadas previamente para la caracterización no destructiva
de diferentes productos cárnicos, podrÃan ser de interés para la detección de pastosidad en jamón.
Diferentes alternativas, como el uso de altas presiones hidrostáticas (HHP) o la aplicación
de tratamientos térmicos de larga duración a baja temperatura (LTLT) al final del proceso de
elaboración del jamón, han sido abordadas previamente para la corrección de pastosidad en jamón
curado. Sin embargo, el elevado coste y el largo tiempo requerido para los tratamientos HHP y
LTLT, respectivamente, pone de manifiesto la necesidad de encontrar alternativas con un coste
moderado y más rápidas.
En este contexto, los principales objetivos de esta tesis fueron determinar la viabilidad de
la utilización de ultrasonidos de baja intensidad para detectar de manera no destructiva la
aparición de pastosidad durante el proceso de elaboración de jamón curado y caracterizar el nivel
de pastosidad en el producto final, asà como explorar la viabilidad de tratamientos térmicos
moderados asistidos por ultrasonidos de alta intensidad para corregir dicho defecto de textura.
Para cumplir el objetivo de caracterizar y corregir el defecto de pastosidad en jamón, se
diseñó y se llevó a cabo un proceso de elaboración para obtener jamones con distintos niveles de
pastosidad sin diferencias considerables del contenido en sal. Durante el procesado, se abordó la
viabilidad de utilizar ultrasonidos por contacto para monitorizar la aparición de la pastosidad. AsÃ,
la velocidad ultrasónica se midió en el jamón fresco, al final de las etapas de salado y postsalado,
3 veces durante el secado-maduración y una vez terminado el proceso de elaboración. Al final del
procesado, también se evaluó el nivel de pastosidad (alto, medio y sin pastosidad) en el jamón loncheado por un panel experto. A medida que avanzó el proceso de elaboración, se observó un
aumento progresivo de la velocidad ultrasónica, de 1536 m/s en jamón fresco hasta 1713 m/s en
jamón curado. Sin embargo, el aumento en la velocidad ultrasónica no se relacionó con el defecto
de pastosidad, probablemente porque los cambios de textura del jamón vinculados con la
pastosidad fueron enmascarados por la gran influencia de los cambios composicionales (ganancia
de sal y pérdida de humedad) en la velocidad ultrasónica. AsÃ, la velocidad ultrasónica no fue un
parámetro útil para detectar la aparición de pastosidad en jamón durante su procesado ni para
clasificar los jamones según su nivel de pastosidad al final del procesado.
Los ultrasonidos por contacto también se utilizaron para monitorizar los cambios
composicionales y texturales que tienen lugar a lo largo de la etapa de postsalado del jamón. Para
ello, se saló otro lote de jamones y se evaluaron distintos tiempos de postsalado, desde 7 hasta 56
dÃas. Durante el postsalado, los jamones se pesaron y se midió su velocidad ultrasónica cada 2
dÃas. Cada 7 dÃas de postsalado, se analizó destructivamente la composición y las propiedades
texturales de un jamón. La pérdida de peso de los jamones durante la etapa de postsalado fue
descrita satisfactoriamente (r=0.95) por el aumento de la velocidad ultrasónica. Además, la
distribución de sal y la pérdida de humedad en el interior del jamón se relacionaron de forma
satisfactoria (r=0.93 y r=0.86, respectivamente) con el aumento de la velocidad ultrasónica. La
variación en la dureza del jamón durante el postsalado fue no significativa y, por ello, el aumento
de la velocidad ultrasónica se atribuyó principalmente a los cambios de composición, siendo
apenas afectada por los cambios de textura.
Los jamones obtenidos con distintos niveles de pastosidad después del proceso de
elaboración, se cortaron y se midió la velocidad y la atenuación ultrasónica del músculo Biceps
femoris con el objetivo de averiguar de forma no destructiva su nivel de pastosidad. Además, con
el fin de analizar mejor este defecto de textura, se analizaron el Ãndice de proteólisis, la
microestructura, la textura instrumental y la composición de los jamones. Las muestras pastosas
presentaron el Ãndice de proteólisis más alto (38.7% comparado con el 33.1% de los jamones no
pastosos), mostraron la degradación estructural más relevante (estructuras miofibrilares
fusionadas y aparición de grandes huecos) y, en consecuencia, fueron las más blandas (5.4 N de
dureza en comparación con los 16.7 N de los jamones no pastosos) y presentaron el
comportamiento viscoso más intenso (0.434 comparado con el 0.372 de los jamones no pastosos),
aunque se encontró una gran variabilidad experimental. La evaluación no destructiva llevada a
cabo mediante ultrasonidos reveló que la atenuación ultrasónica se podrÃa aplicar con éxito para
la clasificación de las lonchas de jamón curado según su nivel de pastosidad. AsÃ, cuanto mayor
fue la pastosidad, mayor fue la atenuación ultrasónica, siendo el coeficiente de atenuación
promedio de las muestras con alta, media y sin pastosidad de 48.2, 45.4 y 43.1 Np/m,
respectivamente. Sin embargo, la velocidad ultrasónica fue muy similar en todas las muestras de jamón, independientemente de su nivel de pastosidad. Como se observó en los jamones enteros,
la velocidad ultrasónica no fue un parámetro útil para cuantificar el defecto de pastosidad en
jamón loncheado, ya que la gran influencia de la composición en la velocidad ultrasónica sumada
al contenido similar de sal y humedad de las muestras, independientemente de su nivel de
pastosidad, dio lugar a una velocidad similar en todos los niveles de pastosidad.
Se desarrollaron dos técnicas de ultrasonidos acoplados por aire, tanto en modo
transmisión-recepción como en pulso-eco, para caracterizar la textura de jamón curado. El
carácter no invasivo de los ultrasonidos acoplados por aire permite llevar a cabo medidas sin
contacto, facilitando su aplicación a nivel industrial en comparación con las técnicas ultrasónicas
convencionales, ya que pueden realizarse medidas a mayor velocidad, sin alterar la superficie del
material y evitando la contaminación cruzada entre alimentos.
En cuanto a las medidas de corrección de defectos texturales en jamón curado, se
evaluaron tratamientos térmicos moderados en dos medios de calentamiento diferentes (agua y
aire). Además, se consideró la viabilidad de intensificar dichos tratamientos mediante la
aplicación de ultrasonidos de alta intensidad (o de potencia). Para ello, se calentaron lonchas de
jamón curado comercial envasadas al vacÃo en medio lÃquido, con y sin la aplicación de
ultrasonidos, a diferentes temperaturas (40, 45 y 50 ºC), midiendo la temperatura en los músculos
Biceps femoris y Semimembranosus. Respecto a los tratamientos en aire, se utilizaron cilindros
de jamón curado comercial envasado al vacÃo. En el primer set de experimentos, el jamón se
calentó a velocidad de aire constante (2 m/s) a diferentes temperaturas (40, 45 y 50 ºC); mientras
que, en el segundo experimento, el jamón se calentó a temperatura de aire constante (50 ºC) a
distintas velocidades (1, 2, 3, 4 y 6 m/s). En los dos sets, los tratamientos se llevaron a cabo con
y sin la aplicación de ultrasonidos de potencia, midiendo la temperatura en el centro del cilindro.
Los tratamientos térmicos se prolongaron hasta alcanzar la temperatura objetivo, definida como
5 ºC por debajo de la temperatura del medio de calentamiento (agua o aire). AsÃ, no se llevó a
cabo una fase de mantenimiento de la temperatura y sólo se consideró la fase de calentamiento de
los tratamientos térmicos. Las cinéticas de calentamiento del jamón tratado tanto en agua como
en aire se describieron matemáticamente considerando que la transferencia de calor estuvo
únicamente controlada por conducción. Una vez finalizado el calentamiento, se evaluaron los
cambios texturales del jamón (dureza y comportamiento elástico). Los experimentos mostraron
que la aplicación de ultrasonidos de potencia aceleró la transferencia de calor, reduciendo
significativamente (p<0.05) el tiempo de calentamiento y aumentando la difusividad térmica
aparente hasta un 51 y 37% en los tratamientos térmicos en agua y aire, respectivamente. En el
caso de los tratamientos térmicos en agua, el aumento de la temperatura durante el calentamiento
provocó una intensificación ultrasónica menor (la difusividad térmica aparente aumentó un 51%
a 40 ºC comparado con el 21% a 50 ºC). Por el contrario, en las experiencias en aire, cuanto mayor fue la temperatura, más efectiva fue la aplicación de los ultrasonidos (la difusividad térmica
aparente incrementó un 5% a 40 ºC comparado con el 38% a 50 ºC). El efecto de la aplicación de
los ultrasonidos disminuyó con el aumento de la velocidad del aire, siendo mÃnimo con la
velocidad de aire más alta ensayada (la difusividad térmica aparente aumentó un 21% a 1 m/s
comparado con el 5% a 6 m/s). En cuanto a los cambios de las propiedades texturales del jamón
después de los tratamientos térmicos moderados limitados a la fase de calentamiento, se observó
un aumento en su dureza y en su comportamiento elástico.
Por último, se abordó la corrección de textura en jamón curado con distintos niveles de
pastosidad. Para ello, se calentaron lonchas de jamón con alta, media y sin pastosidad envasadas
al vacÃo en medio lÃquido a 40 y 50 ºC durante tiempos más largos (5 h, incluyendo las fases de
calentamiento y mantenimiento) que en las experiencias sólo de calentamiento, con y sin la
aplicación de ultrasonidos de potencia únicamente durante la
Automated recognition of lung diseases in CT images based on the optimum-path forest classifier
The World Health Organization estimated that around 300 million people have asthma, and 210 million people are affected by Chronic Obstructive Pulmonary Disease (COPD). Also, it is estimated that the number of deaths from COPD increased 30% in 2015 and COPD will become the third major cause of death worldwide by 2030. These statistics about lung diseases get worse when one considers fibrosis, calcifications and other diseases. For the public health system, the early and accurate diagnosis of any pulmonary disease is mandatory for effective treatments and prevention of further deaths. In this sense, this work consists in using information from lung images to identify and classify lung diseases. Two steps are required to achieve these goals: automatically extraction of representative image features of the lungs and recognition of the possible disease using a computational classifier. As to the first step, this work proposes an approach that combines Spatial Interdependence Matrix (SIM) and Visual Information Fidelity (VIF). Concerning the second step, we propose to employ a Gaussian-based distance to be used together with the optimum-path forest (OPF) classifier to classify the lungs under study as normal or with fibrosis, or even affected by COPD. Moreover, to confirm the robustness of OPF in this classification problem, we also considered Support Vector Machines and a Multilayer Perceptron Neural Network for comparison purposes. Overall, the results confirmed the good performance of the OPF configured with the Gaussian distance when applied to SIM- and VIF-based features. The performance scores achieved by the OPF classifier were as follows: average accuracy of 98.2%, total processing time of 117 microseconds in a common personal laptop, and F-score of 95.2% for the three classification classes. These results showed that OPF is a very competitive classifier, and suitable to be used for lung disease classification
Nondestructive Multivariate Classification of Codling Moth Infested Apples Using Machine Learning and Sensor Fusion
Apple is the number one on the list of the most consumed fruits in the United States. The increasing market demand for high quality apples and the need for fast, and effective quality evaluation techniques have prompted research into the development of nondestructive evaluation methods. Codling moth (CM), Cydia pomonella L. (Lepidoptera: Tortricidae), is the most devastating pest of apples. Therefore, this dissertation is focused on the development of nondestructive methods for the detection and classification of CM-infested apples. The objective one in this study was aimed to identify and characterize the source of detectable vibro-acoustic signals coming from CM-infested apples. A novel approach was developed to correlate the larval activities to low-frequency vibro-acoustic signals, by capturing the larval activities using a digital camera while simultaneously registering the signal patterns observed in the contact piezoelectric sensors on apple surface. While the larva crawling was characterized by the low amplitude and higher frequency (around 4 Hz) signals, the chewing signals had greater amplitude and lower frequency (around 1 Hz). In objective two and three, vibro-acoustic and acoustic impulse methods were developed to classify CM-infested and healthy apples. In the first approach, the identified vibro-acoustic patterns from the infested apples were used for the classification of the CM-infested and healthy signal data. The classification accuracy was as high as 95.94% for 5 s signaling time. For the acoustic impulse method, a knocking test was performed to measure the vibration/acoustic response of the infested apple fruit to a pre-defined impulse in comparison to that of a healthy sample. The classification rate obtained was 99% for a short signaling time of 60-80 ms. In objective four, shortwave near infrared hyperspectral imaging (SWNIR HSI) in the wavelength range of 900-1700 nm was applied to detect CM infestation at the pixel level for the three apple cultivars reaching an accuracy of up to 97.4%. In objective five, the physicochemical characteristics of apples were predicted using HSI method. The results showed the correlation coefficients of prediction (Rp) up to 0.90, 0.93, 0.97, and 0.91 for SSC, firmness, pH and moisture content, respectively. Furthermore, the effect of long-term storage (20 weeks) at three different storage conditions (0 °C, 4 °C, and 10 °C) on CM infestation and the detectability of the infested apples was studied. At a constant storage temperature the detectability of infested samples remained the same for the first three months then improved in the fourth month followed by a decrease until the end of the storage. Finally, a sensor data fusion method was developed which showed an improvement in the classification performance compared to the individual methods. These findings indicated there is a high potential of acoustic and NIR HSI methods for detecting and classifying CM infestation in different apple cultivars
Automated Image Interpretation for Science Autonomy in Robotic Planetary Exploration
Advances in the capabilities of robotic planetary exploration missions have increased the wealth of scientific data they produce, presenting challenges for mission science and operations imposed by the limits of interplanetary radio communications. These data budget pressures can be relieved by increased robotic autonomy, both for onboard operations tasks and for decision- making in response to science data.
This thesis presents new techniques in automated image interpretation for natural scenes of relevance to planetary science and exploration, and elaborates autonomy scenarios under which they could be used to extend the reach and performance of exploration missions on planetary surfaces.
Two computer vision techniques are presented. The first is an algorithm for autonomous classification and segmentation of geological scenes, allowing a photograph of a rock outcrop to be automatically divided into regions by rock type. This important task, currently performed by specialists on Earth, is a prerequisite to decisions about instrument pointing, data triage, and event-driven operations. The approach uses a novel technique to seek distinct visual regions in outcrop photographs. It first generates a feature space by extracting multiple types of visual information from the image. Then, in a training step using labeled exemplar scenes, it applies Mahalanobis distance metric learning (in particular, Multiclass Linear Discriminant Analysis) to discover the linear transformation of the feature space which best separates the geological classes. With the learned representation applied, a vector clustering technique is then used to segment new scenes.
The second technique interrogates sequences of images of the sky to extract, from the motion of clouds, the wind vector at the condensation level — a measurement not normally available for Mars. To account for the deformation of clouds and the ephemerality of their fine-scale features, a template-matching technique (normalized cross-correlation) is used to mutually register images and compute the clouds’ motion.
Both techniques are tested successfully on imagery from a variety of relevant analogue environments on Earth, and on data returned from missions to the planet Mars. For both, scenarios are elaborated for their use in autonomous science data interpretation, and to thereby automate certain steps in the process of robotic exploration
Imaging Sensors and Applications
In past decades, various sensor technologies have been used in all areas of our lives, thus improving our quality of life. In particular, imaging sensors have been widely applied in the development of various imaging approaches such as optical imaging, ultrasound imaging, X-ray imaging, and nuclear imaging, and contributed to achieve high sensitivity, miniaturization, and real-time imaging. These advanced image sensing technologies play an important role not only in the medical field but also in the industrial field. This Special Issue covers broad topics on imaging sensors and applications. The scope range of imaging sensors can be extended to novel imaging sensors and diverse imaging systems, including hardware and software advancements. Additionally, biomedical and nondestructive sensing applications are welcome
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