Skyline Research Articles

Real-Time Infrared Sea–Sky Line Region Detection in Complex Environment Based on Deep Learning

Real-Time Infrared Sea–Sky Line Region Detection in Complex Environment Based on Deep Learning

Constraints on the Spacetime Variation of the Fine-structure Constant Using DESI Emission-line Galaxies

We present strong constraints on the spacetime variation of the fine-structure constant α using the Dark Energy Spectroscopic Instrument (DESI). In this pilot work, we utilize ∼110,000 galaxies with strong and narrow [O iii] λ λ4959, 5007 emission lines to measure the relative variation Δα/α in space and time. The [O iii] doublet is arguably the best choice for this purpose owing to its wide wavelength separation between the two lines and its strong emission in many galaxies. Our galaxy sample spans a redshift range of 0 < z < 0.95, covering half of all cosmic time. We divide the sample into subsamples in 10 redshift bins (Δz = 0.1), and calculate Δα/α for the individual subsamples. The uncertainties of the measured Δα/α are roughly between 2 × 10−6 and 2 × 10−5. We find an apparent α variation with redshift at a level of Δα/α = (2–3) × 10−5. This is highly likely to be caused by systematics associated with wavelength calibration, since such small systematics can be caused by a wavelength distortion of 0.002–0.003 Å, which is beyond the accuracy that the current DESI data can achieve. We refine the wavelength calibration using sky lines for a small fraction of the galaxies, but this does not change our main results. We further probe the spatial variation of α in small redshift ranges, and do not find obvious, large-scale structures in the spatial distribution of Δα/α. As DESI is ongoing, we will include more galaxies, and by improving the wavelength calibration, we expect to obtain a better constraint that is comparable to the strongest current constraint.

A Study on the Regional Evolution of the Hefei Political and Cultural New District Skyline Based on Exploratory Factor Analysis and Semantic Segmentation

The general population’s assessment and perception of a city can be influenced by its skyline, which is one of its representatives. This paper uses semantic segmentation and exploratory factor analysis to conduct a study from two different perspectives, aiming to analyse the development and current situation of the skyline of Hefei’s political and cultural new district. By collecting pictures of the skyline of the New Administrative and Cultural District, the New Administrative and Cultural District of Hefei’s skyline is being studied for overall changes using the semantic segmentation method, and to evaluate the quality of the skyline in various years, the entropy weight–TOPSIS is employed. Through the literature investigation and creation status of the new political and cultural district, the index system is scientifically formulated to conduct a questionnaire survey, and its reliability and validity are tested. This study is conducted with exploratory factor analysis of factors that are vital in the city skyline. The results of this study show that (1) after the semantic segmentation of the pictures, it is found that the proportion of buildings and the proportion of vegetation are both rising; the proportion of buildings tends to level off after 2018, and the proportion of vegetation shows a uniform increase. In the relative proximity ranking, the overall trend is increasing, and the skyline is ranked first in 2024. (2) Two variables were identified based on the findings of the exploratory factor analysis: ‘skyline value’ and ‘neighbourhood ecological quality’. The results of this study show that the skyline of Hefei’s New Administrative and Cultural District in 2024 is the best overall, and that the skyline of the New Administrative and Cultural District has developed into one of the city images of Hefei, and that its optimisation can be considered in terms of the “quality of the surrounding ecological environment”.

Bisection Window and Homogeneity Principle- Based Local Contrast Measure for Infrared Sea–Sky Line Detection

Bisection Window and Homogeneity Principle- Based Local Contrast Measure for Infrared Sea–Sky Line Detection

Multiscale Feature-Based Infrared Ship Detection

In this paper, based on the idea of “step-by-step accuracy”, a novel multiscale feature-based infrared ship-detection method (MSFISD) is proposed. The proposed method can achieve efficient and effective infrared ship detection in complex scenarios, which may provide assistance in applications such as night surveillance. First, candidate regions (CRs) are extracted from the whole image by extracting the sea–sky line and region of interest (ROI). The real sea–sky line is extracted based on the gradient features enhanced by large-scale gradient operators. The coarse segmentation results are obtained by the optimization method and are then refined by incorporating the edge features of the ship to reduce false alarms and obtain the CRs. Second, by analyzing the shape features of ships, the feature quantity is established, and the ships in CRs are finally accurately segmented. Experimental results demonstrate that compared with the other five methods, the proposed method has higher detection accuracy with a lower false-alarm rate and performs better in complex sea scenarios.

Skyline horizon from a mountain 130 km away

How far is the horizon? A photograph of a city skyline taken from a mountain (elevation 1610 m) at a distance of 130 km is used to introduce the question. The formula that relates the distance to the horizon from an elevated observer is easy to derive when refraction is neglected. The observed horizon distance of the skyline is compared with the theoretical horizon limit of this simple formula. Finally, refraction is discussed and shown to increase the limit by about 10%. A highly interactive component making measurements on Google Maps is included. Introductory students at the high school and first-year college level will find this real-life physics application that incorporates photography, geography, online maps, Earth science, and elementary mathematics very stimulating.

Aesthetics Skylines in Manado

The impact of urban development is a change in the face of the city, with various building functions and heights building so that create its skyline Alone. City Manado showing exists growth city in a manner physique and non-physical so that the City of Manado has unknowingly changed the face of the city, especially in the regions Coast. Changes in the face of the city of Manado in the coastal area include changes to the skyline which was originally flat become more expressive when compared to other areas in the city of Manado. The city skyline can be an overview of what is most valued in a city, other than that the beauty of the skyline can only be enjoyed from long distance. Skyline beauty depends on observer perception and the physical form of the city. Research objectives namely to analyze the aesthetic quality of the skyline in the waterfront area of the city of Manado and analyze what factors are there Which shape it. Study This use method qualitative with approach descriptive analysis. The data analysis approach was carried out in a qualitative descriptive manner with the stages of segment division, analysis of the results recording, ground check and analysis of visual element variables. The results showed that: of the seven variables physique skyline aesthetic, only exists five variable which are contained on location study.

Light elements Na and Al in 58 bulge spheroid stars from APOGEE

ABSTRACT We identified a sample of 58 candidate stars with metallicity [Fe/H] ≲ −0.8 that likely belong to the old bulge spheroid stellar population, and analyse their Na and Al abundances from Apache Point Observatory Galactic Evolution Experiment (APOGEE) spectra. In a previous work, we inspected APOGEE-Stellar Parameter and Chemical Abundance Pipeline abundances of C, N, O, Mg, Al, Ca, Si, and Ce in this sample. Regarding Na lines, one of them appears very strong in about 20 per cent of the sample stars, but it is not confirmed by other Na lines, and can be explained by sky lines, which affect the reduced spectra of stars in a certain radial velocity range. The Na abundances for 15 more reliable cases were taken into account. Al lines in the H band instead appear to be very reliable. Na and Al exhibit a spread in abundances, whereas no spread in N abundances is found, and we found no correlation between them, indicating that these stars could not be identified as second-generation stars that originated in globular clusters. We carry out the study of the behaviour of Na and Al in our sample of bulge stars and literature data by comparing them with chemodynamical evolution model suitable for the Galactic bulge. The Na abundances show a large spread, and the chemodynamical models follow the main data, whereas for aluminum instead, the models reproduce very satisfactorily the nearly secondary-element behaviour of aluminum in the metallicity range below [Fe/H] ≲ −1.0. For the lower-metallicity end ([Fe/H &amp;lt; −2.5), hypernovae are assumed to be the main contributor to yields.

Fine-Grained 3D Modeling and Semantic Mapping of Coral Reefs Using Photogrammetric Computer Vision and Machine Learning.

Corals play a crucial role as the primary habitat-building organisms within reef ecosystems, forming expansive structures that extend over vast distances, akin to the way tall buildings define a city's skyline. However, coral reefs are vulnerable to damage and destruction due to their inherent fragility and exposure to various threats, including the impacts of climate change. Similar to successful city management, the utilization of advanced underwater videography, photogrammetric computer vision, and machine learning can facilitate precise 3D modeling and the semantic mapping of coral reefs, aiding in their careful management and conservation to ensure their survival. This study focuses on generating detailed 3D mesh models, digital surface models, and orthomosaics of coral habitats by utilizing underwater coral images and control points. Furthermore, an innovative multi-modal deep neural network is designed to perform the pixel-wise semantic segmentation of orthomosaics, enabling the projection of resulting semantic maps onto a 3D space. Notably, this study achieves a significant milestone by accomplishing semantic fine-grained 3D modeling and rugosity evaluation of coral reefs with millimeter-level accuracy, providing a potent means to understand coral reef variations under climate change with high spatial and temporal resolution.

Analysis and Compensation of Installation Perpendicularity Error in Unmanned Surface Vehicle Electro-Optical Devices by Using Sea–Sky Line Images

As an important sensor of an unmanned surface vehicle (USV), an electro-optical device is usually used to detect ships and obstacles in USV autonomous navigation and collision avoidance. However, the installation perpendicularity error of the electro-optical device greatly impacts the line-of-sight (LOS) stability control. This error is difficult to eliminate through mechanical calibration because the platform inertial navigation axis cannot be led out. This study aims to establish the model for the perpendicularity error of electro-optical devices during circumferential scanning and analyze its impact on the stability of LOS. In addition, we present a measurement technique for perpendicularity errors utilizing sea–sky line images. Through this method, we find an error function of LOS elevation angle, which is a convex function that can quickly search out high-precision perpendicularity errors step by step. Finally, we measured and compensated the perpendicularity error according to experimental data collected by the electro-optical device. The findings of this research demonstrate that the suggested approach can efficiently mitigate low-frequency disruptions and minor amplitude high-frequency vibrations of LOS in the elevation direction. As a result, it considerably enhances the precision of stability and image observation effect of electro-optical devices.

A new quantitative evaluation method of urban skyline based on object-based analysis and constitution theory

The skyline is a comprehensive display of the morphological characteristics and cultural features of a city, and its quantitative evaluation is remarkable for perceiving the city and assisting in its planning. However, previous studies focused on the overall profile or tall buildings, lacking a perspective that considers the composition of skyline objects. This paper proposes a new quantitative method to evaluate the skyline based on the object-based analysis method and the constitution theory. Firstly, the skyline objects, that is, buildings, vegetation and mountains are extracted by using the object-based image analysis method. Secondly, the buildings are further classified into four classes according to their relative height. Then, two quantitative indicators, namely, richness of the object category variety and complexity of the object category spatial distribution, are proposed by considering the constitution theory. Finally, this method is applied to typical urban skylines in Shanghai, Hong Kong, New York and Vancouver. Results show that the new indicators can effectively represent the differences of city skylines when their profile indicators are relatively similar. The method can quantitatively evaluate the composition and spatial distribution of skyline objects. This paper is expected to provide a new perspective on the study of skyline aesthetics.

Ralph L. Sacco, 65, Dies: Stroke Expert With a Talent for Architectural Design.

Ralph L. Sacco, 65, Dies: Stroke Expert With a Talent for Architectural Design.

Ralph L. Sacco, 65, Dies: Stroke Expert With a Talent for Architectural Design.

Ralph L. Sacco, 65, Dies: Stroke Expert With a Talent for Architectural Design.

Infrared Small Dim Target Detection Under Maritime Near Sea–Sky Line Based on Regional-Division Local Contrast Measure

Infrared Small Dim Target Detection Under Maritime Near Sea–Sky Line Based on Regional-Division Local Contrast Measure

Characterizing the circumgalactic medium of quasars at z ∼ 2.2 through H α and Ly α emission

ABSTRACT The discovery of giant quasar Ly α nebulae at z &amp;gt; 2 has opened up the possibility to directly study in emission the Circumgalactic and Intergalactic Medium (CGM/IGM). However, the resonant nature of the Ly α line and its different emission mechanisms hamper the ability to constrain both the kinematics and physical properties of the CGM/IGM. Here, we present results of a pilot project aiming at the detection of CGM H α emission, a line which does not suffer from these limitations. To this end, we first used KCWI to detect Ly α emission around three bright quasars with 2.25 &amp;lt; z &amp;lt; 2.27, a range which is free from bright IR sky lines for H α, and then selected the most extended nebula for H α follow-up with MOSFIRE. Within the MOSFIRE slit, we detected H α emission extending up to 20 physical kpc with a total H α flux of FH α = (9.5 ± 0.9) × 10$^{-18}~\mathrm{erg\, s^{-1}\, cm^{-2}}$. Considering the Ly α flux in the same region, we found FLy α/FH α = 3.7 ± 0.3 consistent with that obtained for the Slug Nebula at z = 2.275 and with recombination radiation. This implies high densities or a very broad density distribution within the CGM of high-redshift quasars. Moreover, the H α line profile suggests the presence of multiple emitting components overlapping along our line of sight and relatively quiescent kinematics, which seems incompatible with either quasar outflows capable of escaping the potential well of the host halo or disc-like rotation in a massive halo (&amp;gt;1012 M⊙).

The Stability of Fiber Spectrographs in the Faint-source Regime

The use of optical fibers in astronomical instrumentation offers high-multiplex and light-gathering flexibility. However, with most previous fiber spectrographs optimized for large fields of view on modest-aperture telescopes, the performance of fibers in the context of faint targets on large telescopes remains largely untested. In this paper, we evaluate aspects of fiber stability, especially as they apply in the context of precision sky subtraction of faint sources at modest spectral resolution (R ∼ 3000). After introducing a framework for describing potential systematic errors, we use publicly available data from existing instruments, including instrumentation used by the fourth-generation Sloan Digital Sky Survey’s MaNGA project (MaNGA: Mapping Nearby Galaxies at Apache Point Observatory) and the Very Large Telescope’s FLAMES: Fiber Large Array Multi Element Spectrograph. We isolate sources of fiber systematics and estimate the observed amplitude of persistent residuals as well as stochastic noise contributions resulting from changing fiber stresses. Comparing these levels against their impact on various sky subtraction schemes demonstrates that 0.1% precision sky subtraction with fiber instruments is possible. As a demonstration, we show that the MaNGA instrument can deliver 0.2% residuals on bright near-IR sky lines with nonlocal sky subtraction, if pseudo-slit limitations are addressed by allocating 50% of its fibers to sky. We further highlight recently published deep exposures that achieved a 1σ background level of 27.6 AB per square arc second, equivalent to a precision of 0.2% of the sky background continuum.

Proposing Cubic-Grid System as a New Structural System for Tall Buildings

Background: Changes in the skyline of cities all over the world show that tall buildings are an interesting solution to accommodating growth more sustainably in today’s urban areas. Stability against lateral loading is the main issue for designing high-rise buildings. Diagrid systems or grid structures are one of these stable systems. For a long time, the only structural pattern used in this system was the triangular modulus (diagrid). Methods: In the present study, a new pattern for grid structures was introduced, and its performance was compared with the two previous common patterns (triangular and hexagonal). The new pattern is called the Isometric Cube grid, thanks to its particular shape. The design process was performed based on a simple stiffness criterion presented in the previous research. In order to calculate the stiffness of the structure for the new pattern, two types of existing structural nodes were distinguished, and the results were combined to determine the stiffness of the unit forming the entire grid. Results and Conclusion: From the results of analysis, it was found that the optimal angles of diagonal elements were in the range of 50-65 degrees. Although the behavior of the new pattern in terms of shear stiffness was between the two previous patterns (and closer to the hexagonal pattern), the shear stiffness ratio increased from 30° to 65° for cube pattern, while for hexagrid, it decreased over the same range of angles.

The tactics of illumination of high-rise buildings in the cities skyline. Research by design on Skyreach tower skyscraper in Warsaw

ABSTRACT The evening and night silhouette of the city differs from daytime views and is recognizable by the illumination of the buildings. The text refers to the theoretical issues and research by design related to the illumination project of the Skyreach skyscraper building located at ul. Grzybowska 59. The criteria to light the building at night and the methodology of designing the illumination of buildings in terms of architecture are introduced. The research results are presented. The proposed methodology includes carrying out an analysis of the visibility of the city panorama and the illuminated building from key vantage points and key observation plans for the designed building, the role of illuminated buildings in spatial orientation, lighting colours, aspects of connecting lighting with the nature of the illuminated building, lighting intensity and light sources. All these issues were taken into account when designing the illumination of a high-rise building in an urban environment, especially, as in the case of Warsaw, in the absence of municipal guidelines regarding the illumination strategy of the city skyline. Since shortly, in connection with the rapid development of LED and OLED lighting, a large impact of building illumination on the appearance of the city should be expected, therefore the right tactics in carrying out the project of illuminating high-rise buildings, is important, which is diagnosed in the text.

Balancing Cultural Heritage Conservation: Visual Integrity Assessment to Support Change Management in the Buffer Zone of Chiang Mai Historic City Using GIS and Computer-Generated 3D Modeling

The cultural landscape of Chiang Mai city, which is characterized by the interlinkage between mountain and historical settlement, has faced the adverse impacts of visual intrusion in its buffer zone from urbanization. However, there are challenges to creating a quantitative visual evaluation for decision making in response to rapid urban change. This study evaluated the impact of building height on the city skyline and utilized existing cultural heritage locations on the mountain to define a protected visual zone while conducting a 3D-GIS-based visibility analysis to identify obstruction in three scenarios: the actual condition scenario (ACS) considering current conditions, the land use scenario (LUS) considering the land use ordinance, and the proposed scenario (PPS) considering mountain skyline protection, using computer-generated 3D city modeling. The comparative results from the analysis of viewshed, line of sight, and development area calculations revealed that the number of obstructed locations in the LUS decreased by 48.46%, and in the PPS, they decreased by 77.99%, while the development area increased by similar amounts, demonstrating that the city can grow and develop despite stricter height controls. In addition, based on a visual assessment, this study established a buffer distance and intensity to protect the integrity of the heritage while allowing the city to develop.

A Hierarchical Stabilization Control Method for a Three-Axis Gimbal Based on Sea–Sky-Line Detection

Obtaining a stable video sequence for cameras on surface vehicles is always a challenging problem due to the severe disturbances in heavy sea environments. Aiming at this problem, this paper proposes a novel hierarchical stabilization method based on real-time sea–sky-line detection. More specifically, a hierarchical image stabilization control method that combines mechanical image stabilization with electronic image stabilization is adopted. With respect to the mechanical image stabilization method, a gimbal with three degrees of freedom (DOFs) and with a robust controller is utilized for the primary motion compensation. In addition, the electronic image stabilization method based on sea–sky-line detection in video sequences accomplishes motion estimation and compensation. The Canny algorithm and Hough transform are utilized to detect the sea–sky line. Noticeably, an image-clipping strategy based on prior information is implemented to ensure real-time performance, which can effectively improve the processing speed and reduce the equipment performance requirements. The experimental results indicate that the proposed method for mechanical and electronic stabilization can reduce the vibration by 74.2% and 42.1%, respectively.