•The variation of the craters generated by fs laser irradiation with repetition rate is investigated.•The influence of the laser pulse repetition rate on removal rate and surface texture on silicon ...is addressed.•Possible effects of plume shielding on crater features and laser surface structuring at high repetition rate is discussed.
The influence of the pulse repetition rate on laser irradiation of silicon, in air, with femtosecond laser pulses is experimentally investigated in the range 10 Hz – 200 kHz. The features of the produced crater and the laser-induced periodic surface structures generated on its surface are characterized by exploiting surface profilometry and scanning electron microscopy. The experimental characterization evidences an interesting influence of the pulse repetition rate on the crater size qualitatively addressing a progressive reduction of the material removal efficiency at higher repetition rates. Moreover, also the surface structures produced by an irradiation sequence with a fixed number of laser pulses (namely N = 100) shows a clear dependence on the repetition rate. The observed effects are rationalized by considering the possible influence of plume shielding and heat accumulation effects typically observed during laser processing with high repetition rate laser systems.
The preparation of control data is a primary concern in many supervised classification schemes. In coral reef mapping, this issue becomes more severe for three reasons: (1) control samples, located ...beneath the water, are quite difficult and costly to access; (2) because of the high spatial variability of coral reef habitats, it is very difficult to obtain high-quality samples; and (3) pure training samples are also hardly achievable. These issues, namely quantity, quality, and impurity challenges, are the main focus of this study. Three classification algorithms, including Maximum Likelihood Classifier (MLC), Artificial Neural Networks (ANNs), and Support Vector Machines (SVMs), are comprehensively evaluated, and their requirements for control data are determined. To accomplish this, rich field data, collected from diving off of Lizard Island in eastern Australia, and Landsat-8 images are used as the input data. With respect to accuracy, ANN is best, as it can deal with the complexity of coral reef environments; however, it requires a higher number of training samples (i.e. ANN cannot manage the quantity challenge). On the other hand, SVM shows the best resistance against the quantity and impurity challenges. Being aware of these points, a coral reef map is produced, for the first time, of the northern Persian Gulf, a coral habitat with very special environmental conditions. In this region, SVM achieved 68.42% overall accuracy, even though a very limited field work campaign was conducted to provide the control data.
Soil lead content is an important parameter in environmental and industrial applications. Chemical analysis, the most commonly method for studying soil samples, are costly, however application of ...soil spectroscopy presents a more viable alternative. The first step in the method is usually to extract some appropriate spectral features and then regression models are applied to these extracted features. The aim of this paper was to design an accurate and robust regression technique to estimate soil lead contents from laboratory observed spectra. Three appropriate spectral features were selected according to information from other research as well as the spectrum interpretation of field collected soil samples containing lead. These features were then applied to common Multiple Linear Regression (MLR), Partial Least Square Regression (PLSR) and Neural Network (NN) regression models. Results showed that although NN had adequate accuracy, it produced unstable results (i.e., variation of response in different runs). This problem was addressed with application of a Fuzzy Neural Network (FNN) with a least square training strategy. In addition to the stabilized and unique response, the capability of the proposed FNN was proved in terms of regression accuracy where a Ratio of Performance to Deviation (RPD) of 8.76 was achieved for test samples.
We present a detailed study of the excited state properties of 5-benzyluracil (5BU) in the gas phase and in implicit solvent using different electronic structure approaches ranging from ...time-dependent density functional theory in the linear response regime (LR-TDDFT) to a set of different wave-function-based methods for excited states, namely perturbed coupled cluster (CC2), algebraic diagrammatic construction method to second order (ADC(2)), and perturbed configuration interaction (CIS(D)). 5BU has been used to investigate DNA base–amino acid interactions. In particular, it served as a model of protein–DNA photoinduced cross-linking. While LR-TDDFT is computationally the most efficient first-principles approach for static and dynamic simulations of this bichromophoric system, its accuracy is difficult to assess due to the presence of excited states with charge transfer character. In this work, the performance of different exchange correlation functionals is compared against accurate benchmarks obtained either from high level wave-function-based methods or directly from experimental absorption spectra. Our investigation shows that accurate results for the excitation energies can be obtained using the hybrid meta-GGA functional M06. In view of dynamical studies of the relaxation of 5BU after photoexcitation, we also show that the PBE functional, while failing in the Franck–Condon region, provides qualitatively good results for the characterisation of a possible photocyclization path.
A novel technique was demonstrated that overcomes important drawbacks to crosslink cells by irradiation with ultrashort ultraviolet laser pulses (L-crosslinking). To use this technique coupled to ...Chromatin ImmunoPrecipitation (ChIP) in a high throughput context, a prescreening fast method needs to be implemented to set up suitable irradiation conditions of the cell sample for efficient L-crosslinking with no final and long ChIP analysis. Here a fast method is reported where living human cells have been first transfected with a vector coding for Estrogen Receptor α (ERα), linked to Green Florescent protein (ERα-GFP), so that the well-known interaction between the Estrogen Receptor Elements (ERE) region of the cell DNA and the ERα protein can be detected by studying the fluorometric response of the irradiated cells. The damage induced to cells by ultraviolet irradiation is characterized by looking at the DNA integrity, protein stability, and cellular viability. A second novel approach is presented to analyze or re-visit DNA and RNA sequences and their molecular configurations. This approach is based on methods derived from Chern-Simons super-gravity adapted to describe mutations in DNA/RNA strings, as well as interactions between nucleic acids. As a preliminary case, we analyze the KRAS human gene sequence and some of its mutations. Interestingly, our model shows how the Chern-Simons currents are able to characterize the mutations within a sequence, in particular giving a quantitative indication of the mutation likelihood.
•The effect of the LIPSS process on the surface chemical properties and consequently on SEY is investigated.•Femtosecond Laser-Induced Periodic Surface Structures (LIPSS) are used to reduce SEY in ...copper.•Copper treated with LIPSS shows a low surface debris density and is therefore less critical for ultra-high vacuum applications in particle accelerators.
The electron-cloud phenomenon is one cause of beam instabilities in high intensity positive particle accelerators. Among the proposed techniques to mitigate or control this detrimental effect, micro-/nano-geometrical modifications of vacuum chamber surfaces are promising to reduce the number of emitted secondary electrons. Femtosecond laser surface structuring readily allows the fabrication of Laser Induced Periodic Surface Structures (LIPSS) and is utilized in several fields, but has not yet been tested for secondary electron emission reduction. In this study, such treatment is carried out on copper samples using linearly and circularly polarized femtosecond laser pulses. The influence of the formed surface textures on the secondary electron yield (SEY) is studied. We investigate the morphological properties as well as the chemical composition by means of SEM, AFM, Raman and XPS analyses. Surface modification with linearly polarized light is more effective than using circularly polarized light, leading to a significant SEY reduction. Even though the SEY maximum is only reduced to a value of ~1.7 compared to standard laser-induced surface roughening approaches, the femtosecond-LIPSS process enables to limit material ablation as well as the production of undesired dust, and drastically reduces the number of redeposited nanoparticles at the surface, which are detrimental for applications in particle accelerators. Moreover, conditioning tests reveal that LIPSS processed Cu can reach SEY values below unity at electron irradiation doses above 10−3 C/mm2.
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The estimation of cultivation area and categorizing the agricultural product types is one of the prerequisites for achieving sustainable development in the agricultural studies. In this study, an ...unsupervised zoning the cultivation areas with the same cultivation pattern in Golestan province is on the agenda. Therefore, due to wide spatial range, high temporal resolution and easy access of 16-day products of the vegetation of the MODIS sensor which acquired in a year (From November 2017 to October 2018), these images are used in this research. In the proposed method, after the generating of NDVI vegetation time series as a hyper-cube and separating farmlands’ boundaries in Golestan province using the land-use map; the Sequential Maximum Angle Convex Cone (SMACC) endmember extraction algorithm and the maximum number of product variation using the statistical information of the region (Obtained from the statistics centre of Iran) are used to extract endmembers of the hyper-cube. In the following, the timing responses of the NDVI, identified as endmembers, will be refined in the second phase. In this process, identifying and eliminating noise signals (unrelated to cultivating patterns) and integrating the same cultivating patterns will be on the agenda. At the last stage of the proposed method and after refinement of the endmembers, the hyper-cube is clustered by Spectral Angle Mapper (SAM) algorithm and the mapping of regions with the same cultivation pattern is produced. In the proposed method, the zoning of agricultural land is based solely on the statistical knowledge of the variety of cultivation and the results have led to the production of interconnected spatial parts. This is consistent with the reality of the spatial occurrence of similar cultivating patterns in a geographic area. On the other hand, the visual comparison of results with large scale satellite images illustrates that there is a significant relationship between clustering results and ground truth in terms of cultivating pattern. Obviously, such products can be used as initial layers of information to produce the results of a supervised classification with the aim of applying the cultivation area of a variety of agricultural products.
IMPROVING LINEAR SPECTRAL UNMIXING THROUGH LOCAL ENDMEMBER DETECTION Ramak, R.; Valadan Zouj, M. J.; Mojaradi, B.
International archives of the photogrammetry, remote sensing and spatial information sciences.,
01/2015, Letnik:
XL-3/W2, Številka:
3
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
There are a considerable number of mixed pixels in remotely sensed images. Different sub-pixel analyses have been recently developed correspondingly. A well-known method is linear spectral unmixing ...which obtains an abundance of each endmember in a given pixel. This model assumes that each pixel is a linear combination of all endmembers in a scene. This assumption is not correct since each pixel can only be a composition of some surrounding endmembers. Even though, a fully mathematical technique is used for spectral analysis, the output of the model may not represent the physical nature of the objects over the pixel under test. In this regard, this paper proposes a Local Linear Spectral Unmixing which is based on neighbor pixels classes. Having classified the image, using a supervised classifier, it is scanned through a window of an appropriate size. For each pixel at the center of the window, the endmember matrix is formed only based on the majority classes existed in the window. Then the amount of each one is calculated. The LLSU method was evaluated on an AVIRIS data set collected from an agricultural area of northern Indiana. The results of the proposed method demonstrate a significant improvement in comparison with the LSU results. Moreover, due to the dimension reduction of the endmember matrix in this method, the computation time of the LLSU speeds up by three to eight times compared to the conventional Linear Spectral Unmixing method. As a result, the proposed method is efficient over the spectral unmixing tasks.
3D Building Reconstruction Using Dense Photogrammetric Point Cloud Malihi, S.; Valadan Zoej, M. J.; Hahn, M. ...
International archives of the photogrammetry, remote sensing and spatial information sciences.,
01/2016, Letnik:
XLI-B3
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
Three dimensional models of urban areas play an important role in city planning, disaster management, city navigation and other applications. Reconstruction of 3D building models is still a ...challenging issue in 3D city modelling. Point clouds generated from multi view images of UAV is a novel source of spatial data, which is used in this research for building reconstruction. The process starts with the segmentation of point clouds of roofs and walls into planar groups. By generating related surfaces and using geometrical constraints plus considering symmetry, a 3d model of building is reconstructed. In a refinement step, dormers are extracted, and their models are reconstructed. The details of the 3d reconstructed model are in LoD3 level, with respect to modelling eaves, fractions of roof and dormers.
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