Number Of Tiles Research Articles

STC: FoV Tracking Enabled High-Quality 16K VR Video Streaming on Mobile Platforms

The ultra-high-definition 16K Virtual Reality (VR) video is coming to ages with more ”real” virtual experience and less cybersickness. However, the huge bitrate and decoding overhead would overwhelm today’s network and mobile hardware. The widely-known Field-of-View (FoV) adaptation streaming method still has severe bitrate wastes and decoding overhead as it delivers FoV areas with grid-like static tiles. Inspired by this, we present a novel ShiftTile-traCking (STC) streaming scheme, which crops and delivers tiles by tracking FoV movement. It is equivalent to deliver an FoV planar video instead of VR videos. This would save huge bit-rate and reduce decoding complexity. We mainly entail three contributions. 1) To reduce projection distortions, a novel FoV-centric sphere projection is proposed, which projects VR videos with the center of users’ FoVs. 2) To cover diverse FoV movement trajectories with a limited number of tiles, we propose an optimal tiling algorithm by trajectory clustering. 3) To be resilient to FoV prediction errors, we propose an accuracy-sensitive streaming algorithm, which scales FoV areas by the prediction accuracy. The evaluation shows that under the same network conditions, STC improves up to 1.3dB V-PSNR, reduces up to 13.2% buffering ratio, and achieves 60% faster decoding speed (61.5 frames per second) compared with state-of-the-art solutions.

Effect of impurities on tiling in a two-dimensional dodecagonal quasicrystal

Langevin dynamics simulations are performed to examine how impurities affect two-dimensional dodecagonal quasicrystals. We assumed that the interaction potential between two particles is the Lennard–Jones–Gauss potential if at least one of these particles is a matrix particle and that the interaction potential between two impurities is the Lennard–Jones potential. Matrix particles and impurities impinge with constant rates on the substrate created by a part of a dodecagonal quasicrystal consisting of square and triangular tiles. The dependences of the twelve-fold rotational order and the number of shield-like tiles on the impurity density are examined after sufficient solid layers are grown. While the change in the twelve-fold rotational symmetry is small, the number of shield-like tiles in the solid increases greatly with increasing impurity density.

Learned Multiagent Real-Time Guidance with Applications to Quadrotor Runway Inspection

Aircraft runways are periodically inspected for debris and damage. Instead of having pilots coordinate the motion of the quadrotors manually or hand-crafting the desired quadrotor behavior into a guidance law, this paper reports the use of deep reinforcement learning to learn a closed-loop multiagent real-time guidance strategy for quadrotors to autonomously perform such inspections. This yields a significant reduction in engineering effort while enabling highly-flexible real-time performance. The runway is discretized into a number of rectangular tiles, which must all be visited for the runway to be considered inspected. The guidance system reported here calculates a desired acceleration in real time for the quadrotor(s) to track in order to complete the task. This paper first develops the guidance technique, trains it in simulation, and evaluates it experimentally using an indoor quadrotor laboratory. This process is then repeated for an outdoor setting on a real runway, where the proposed guidance strategy is compared to a handcrafted strategy and applied to a multiquadrotor scenario where the quadrotors must learn to coordinate their behavior and be resilient to the failure of one quadrotor mid-experiment. Multiagent, fault-tolerant, learned behavior is successfully demonstrated through outdoor quadrotor flights. Additional simulations and experiments demonstrate the technique is viable in a swarm with additional quadrotors, on a variety of runway shapes and with increased discretization of the runway. This work shows how modern learning-based techniques can: 1) reduce the engineering effort required to design complex guidance systems and 2) be implemented on real hardware in a representative outdoor environment.

Lozenge tilings of hexagons with holes on three crossing lines

The enumeration of lozenge tilings of hexagons with holes has received much attention during the last three decades. One notable feature is that a lot of the recent development involved Kuo's graphical condensation. Motivated by Ciucu, Lai and Rohatgi's work on tilings of hexagons with a removed triad of bowties, in this paper, we show that the ratio of numbers of lozenge tilings of two more general regions is expressed as a simple product formula. Our proof does not involve the graphical condensation method. The proof is short and direct. We also provide a corresponding formula for cyclically symmetric lozenge tilings. Several previous results can be easily deduced from our generalization.

Energy generation in public buildings using piezoelectric flooring tiles; A case study of a metro station

The building sector is benefitting from the significant advancements in clean energy harvesting technologies. The function of building products is witnessing a huge leap to extend beyond mere functional requirements to account for the environmental benefit as well. Piezoelectric flooring tiles are amongst the most promising for indoor energy generation especially in public buildings with great occupancy patterns and intensity. Hence, this study presents a comprehensive review of literature for the use of piezoelectric. The next step deducted parameter integration for the proper selection of piezoelectric tiles. This determined its successful application in the building industry-especially the transportation section which has a notable contribution to energy consumption and emission release. These were divided into factors related to the project type and location, as well as proper selection of the piezoelectric tile product. This hypothesis was tested in the case study. Hence, the application of piezoelectricity was investigated in a Metro station in a core urban area in Egypt, with an estimate of almost 57,000 daily passengers. The selection of the metro line and station as well as the location of installing the tiles was based on the highest passenger density class which provided the greatest step-footage. Furthermore, the selection of the number and type of piezoelectric tiles was determined based on the current project's energy consumption. The study compared the two shortlisted types of tiles in terms of their power generation capacity, initial capital cost, lifespan and expected savings. The results showed that twelve tiles were needed to generate the station's needs for electric energy using Sustainable Energy Floor tiles while only eight tiles were needed using Waynergy piezoelectric tiles. The results also showed a decrease in energy consumption and carbon emissions.

Viewport-Aware Deep Reinforcement Learning Approach for 360$^\circ$ Video Caching

360<inline-formula><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> video is an essential component of VR/AR/MR systems that provides immersive experience to the users. However, 360<inline-formula><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> video is associated with high bandwidth requirements. The required bandwidth can be reduced by exploiting the fact that users are interested in viewing only a part of the video scene and that users request viewports that overlap with each other. Motivated by the findings of our recent works where the benefits of caching video tiles at edge servers instead of caching entire 360<inline-formula><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> videos were shown, in this paper, we introduce the concept of virtual viewports that have the same number of tiles with the original viewports. The tiles forming these viewports are the most popular ones for each video and are determined by the users&#x2019; requests. Then, we propose a reactive caching scheme that assumes unknown videos&#x2019; and viewports&#x2019; popularity. Our scheme determines which videos to cache as well as which is the optimal virtual viewport per video. Virtual viewports permit to lower the dimensionality of the cache optimization problem. To solve the problem, we first formulate the content placement of 360<inline-formula><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> videos in edge cache networks as a Markov Decision Process (MDP), and then we determine the optimal caching placement using the Deep Q-Network (DQN) algorithm. The proposed solution aims at maximizing the overall quality of the 360<inline-formula><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> videos delivered to the end-users by caching the most popular 360<inline-formula><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> videos at base quality along with a virtual viewport in high quality. We extensively evaluate the performance of the proposed system and compare it with that of known systems such as Least Frequently Used (LFU), Least Recently Used (LRU), First In First Out (FIFO), over both synthetic and real 360<inline-formula><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> video traces. The results reveal the large benefits coming from reactive caching of virtual viewports instead of the original ones in terms of the overall quality of the rendered viewports, the cache hit ratio, and the servicing cost.

Crossings. Flying Over Antisymmetric Truchet Friezes

Symmetry and antisymmetry are resources used by humans since pre-historic times in their artistic creations. In this work we start by introducing antisymmetry and the 17 possible asso- ciated groups. We then present some counts of friezes, built with a particular module, the Truchet tile, which is itself antisymmetric. These counts take into consideration the frieze antisymmetry group and the number of tiles composing the unitary cell which originates the frieze by translation. These Truchet friezes led to the creation of a set of 5 paintings, named Crossings, which illustrate all the possible groups, in an artistic context.

Pointwise periodic maps with quantized first integrals

We describe the global dynamics of some pointwise periodic piecewise linear maps in the plane that exhibit interesting dynamic features. For each of these maps we find a first integral. For these integrals the set of values are discrete, thus quantized. Furthermore, the level sets are bounded sets whose interior is formed by a finite number of open tiles of certain regular or uniform tessellations. The action of the maps on each invariant set of tiles is described geometrically.

The Influence of Marina Characteristics on Non-native Colonisation

The marina properties, such as; salinity range, tidal fluctuations, depth, and ascidian presence in-fluence the distribution of invasive non-natives. Transport vectors, aquaculture and fishery practic-es also have an important role in the distribution of invasive non-native species during the bioinva-sion process. We focused on 10 invasive non-native species of marine invertebrates in the UK. This study explained the distribution and ecology of five invasive non-native species (Styela clava (As-cidia), Didemnum vexillum (Ascidia), Caprella mutica (Crustacea), Crepidula fornicata (Gastropo-da), Watersipora subtorquata (Bryozoa)) and the marina characteristics of five invasive non-native species colonization (Austrominius modestus (Arthropoda), Ciona intestinalis (Ascidia), Botrylloides violaceus (Ascidia), Tricellaria inopinata (Bryozoa), Bugula neritina (Bryozoa)) in Wales coasts. The study site deployed settlement tiles in the inner and the outer tile as two positions in each marina: An equal number of vertical and horizontal tiles was deployed at each site with half-sampled at two weeks (very early colonization) and at eight weeks (later colonization). The results showed that some variations in marina characteristics affected the distribution of invasive non-native species. Invasive non-native species abundance, diversity and multivariate structure of the assemblages were very high. The colonization of tiles varied between locations at the entrance and within the marina, but not in any way, and the effect of tile orientation was surprisingly low.

Twenty Vertex Model and Domino Tilings of the Aztec Triangle

We show that the number of configurations of the 20 Vertex model on certain domains with domain wall type boundary conditions is equal to the number of domino tilings of Aztec-like triangles, proving a conjecture of the author and Guitter. The result is based on the integrability of the 20 Vertex model and uses a connection to the U-turn boundary 6 Vertex model to re-express the number of 20 Vertex configurations as a simple determinant, which is then related to a Lindström-Gessel-Viennot determinant for the domino tiling problem. The common number of configurations is conjectured to be $2^{n(n-1)/2}\prod_{j=0}^{n-1}\frac{(4j+2)!}{(n+2j+1)!}=1, 4, 60, 3328, 678912...$ The enumeration result is extended to include refinements of both numbers.

Parameter selection for CLAHE using multi-objective cuckoo search algorithm for image contrast enhancement

Contrast enhancement techniques that are proposed in the literature are devised to enhance image quality so as to provide better details for different image processing tasks. Histogram Equalization (HE) is a widely exploited technique to enhance contrast of the images. Histograms are used to measure the frequency of intensity levels in an image. The objective of HE is to distribute the intensity values in an image such that the lower contrast areas can gain higher contrast. HE techniques can be global or local. The Contrast Limited Adaptive Histogram Equalization (CLAHE) is a local HE method. Thus, CLAHE can handle the problems of the classical HE algorithm. CLAHE employs two parameters, which are, respectively, number of tiles and clip limit. The efficiency of the CLAHE depends on these two parameters. Hence, the results can be changed if the parameters of the CLAHE is adjusted. The value of the optimal parameters can vary according to the image type. In this paper, Multi-objective Cuckoo Search (MOCS) is employed to determine optimal parameters for CLAHE to enhance the contrast of images. For MOCS, first fitness function is set for computing Entropy and second fitness function is set for computing Fast Noise Variance Estimation (FNVE) so as to provide a good local detail preservation and prevent noise amplification in the output image. Image dataset is taken from Contrast Enhancement Evaluation Database (CEED2016), which can be found in Mendeley data repository. This database is used for evaluating the overall performance of the proposed method. Evaluation results of the proposed method are given in terms of Absolute Mean Brightness Error (AMBE), Peak Signal-to-noise Ratio (PSNR), Mean Squared Error (MSE), Maximum Difference (MD), Mean Absolute Error (MAE) and Computing Time (CT) .

Pinpointing optimized air quality model performance over the Beijing-Tianjin-Hebei region: Mosaic approach

Mosaic approach, with certain number of tiles representing land use (LU) types in each grid cell, had been implemented into WRF-Noah model. Previous studies found mosaic approach had a better performance on meteorological parameters than only considering dominant LU in dominant approach. In this study, the impacts of mosaic approach on meteorological parameters and air quality were investigated in WRF-CMAQ over Beijing-Tianjin-Hebei (BTH) region in China in 2020. Results showed that mosaic approach improved the simulation results of WS10 (surface wind speed at 10 m), T2 (temperature at 2 m), and RH (relative humidity) especially in nighttime in winter and were available for all stations with different percent of urban area. “MOS_TOPO” scenario, which coupled with mosaic approach and “topo-wind” schemes, obtained best simulation results of WS10 and T2 in January among six scenarios, with the lower average Root Mean Square Error of WS10 (1.18 m/s) and Mean Bias of T2 (0.55 °C) for all stations. Meanwhile, mosaic approach obtained lower |NMB| of PM2.5 than dominant approach in more than 69% cities in BTH region. Cities in southern Hebei province, especially Xingtai city, were identified as the most sensitive area for PM2.5 simulation affected by mosaic approach. Although the mosaic approach has improved the simulation results of meteorological parameters, especially the nighttime simulation results of WS10, there is still some deviation in the simulation results of PM2.5. Accurate emission inventory, suitable physics option in numerical weather model and rational chemical mechanism in air quality model are the important factors for WRF-CMAQ.

Google Earth Engine for large-scale land use and land cover mapping: an object-based classification approach using spectral, textural and topographical factors

ABSTRACT Mapping the distribution and type of land use and land cover (LULC) is essential for watershed management. The Tigris-Euphrates basin is a transboundary region in the Middle East shared between six countries, but a recent fine-scale LULC map of the area is lacking. Using Landsat-8 time series, a 30-m resolution LULC map was produced for the Tigris-Euphrates basin. In total, 1184 Landsat scenes were processed within the Google Earth Engine (GEE). For the collection of ground truth data, differential manifestations of green cover were considered by dividing the study area into five climatic regions and the training samples were taken from each sub-region. To account for the temporal variation of LULC types, six two-month interval composite layers, including the spectral and thermal bands of Landsat-8, texture and spectral indices, as well as topographic factors were created for the target year 2019. Image segmentation and classification were performed using the simple non-iterative clustering (SNIC) and Random Forest (RF) algorithms, respectively. A computationally effective parallel processing approach was developed, which created a number of tiles and sub-tiles and a bulk command was converted into smaller parallel commands. The generated LULC map showed a satisfactory overall accuracy of 91.7%, with the highest User’s accuracy in water and wetland, and the lowest in rainfed crop and rangeland and the highest Producer’s accuracy in water and barren areas, and the lowest in garden and rangeland. This study highlights the necessity of using multi-temporal data for LULC mapping, in particular, multi-temporal NDVI, for the separation of different green cover types in arid and semi-arid environment.

Unconventional patterns on surfaces

We present a unified method to meshing surfaces with unconventional patterns, both periodic and aperiodic. These patterns, which have so far been studied on the plane, are patterns comprising a small number of tiles, that do not necessarily exhibit translational periodicity. Our method generalizes the de Bruijn multigrid method to the discrete setting, and thus reduces the problem to the computation of N -Directional fields on triangle meshes. We work with all cases of directional symmetries that have been little studied, including odd and high N. We address the properties of such patterns on surfaces and the challenges in their construction, including order-preservation, seamlessness, duality, and singularities. We show how our method allows for the design of original and unconventional meshes that can be applied to architectural, industrial, and recreational design.

15-Puzzle Problem Solving with the Artificial Bee Colony Algorithm Based on Pattern Database

The N-puzzle problem is one of the most classical problems in mathematics. Since the number of states in the N-puzzle is equal to the factorial of the number of tiles, traditional algorithms can only provide solutions for small-scale ones, such as 8-puzzle. Various uninformed and informed search algorithms have been applied to solve the N-puzzle, and their performances have been evaluated. Apart from traditional methods, artificial intelligence algorithms are also used for solutions. This paper introduces a new approach based on a meta-heuristic algorithm with a solving of the 15-puzzle problem. Generally, only Manhattan distance is used as the heuristic function, while in this study, a linear conflict function is used to increase the effectiveness of the heuristic function. Besides, the puzzle was divided into subsets named pattern database, and solutions were obtained for the subsets separately with the artificial bee colony (ABC) algorithm. The proposed approach reveals that the ABC algorithm is very successful in solving the 15-puzzle problem.

Channels, Billiards, and Perfect Matching 2-Divisibility

Let $m_G$ denote the number of perfect matchings of the graph $G$. We introduce a number of combinatorial tools for determining the parity of $m_G$ and giving a lower bound on the power of 2 dividing $m_G$. In particular, we introduce certain vertex sets called channels, which correspond to elements in the kernel of the adjacency matrix of $G$ modulo $2$. A result of Lovász states that the existence of a nontrivial channel is equivalent to $m_G$ being even. We give a new combinatorial proof of this result and strengthen it by showing that the number of channels gives a lower bound on the power of $2$ dividing $m_G$ when $G$ is planar. We describe a number of local graph operations which preserve the number of channels. We also establish a surprising connection between 2-divisibility of $m_G$ and dynamical systems by showing an equivalency between channels and billiard paths. We exploit this relationship to show that $2^{\frac{\gcd(m+1,n+1)-1}{2}}$ divides the number of domino tilings of the $m\times n$ rectangle. We also use billiard paths to give a fast algorithm for counting channels (and hence determining the parity of the number of domino tilings) in simply connected regions of the square grid.

Assessing Deep Convolutional Neural Networks and Assisted Machine Perception for Urban Mapping

High-spatial-resolution satellite imagery has been widely applied for detailed urban mapping. Recently, deep convolutional neural networks (DCNNs) have shown promise in certain remote sensing applications, but they are still relatively new techniques for general urban mapping. This study examines the use of two DCNNs (U-Net and VGG16) to provide an automatic schema to support high-resolution mapping of buildings, road/open built-up, and vegetation cover. Using WorldView-2 imagery as input, we first applied an established OBIA method to characterize major urban land cover classes. An OBIA-derived urban map was then divided into a training and testing region to evaluate the DCNNs’ performance. For U-Net mapping, we were particularly interested in how sample size or the number of image tiles affect mapping accuracy. U-Net generated cross-validation accuracies ranging from 40.5 to 95.2% for training sample sizes from 32 to 4096 image tiles (each tile was 256 by 256 pixels). A per-pixel accuracy assessment led to 87.8 percent overall accuracy for the testing region, suggesting U-Net’s good generalization capabilities. For the VGG16 mapping, we proposed an object-based framing paradigm that retains spatial information and assists machine perception through Gaussian blurring. Gaussian blurring was used as a pre-processing step to enhance the contrast between objects of interest and background (contextual) information. Combined with the pre-trained VGG16 and transfer learning, this analytical approach generated a 77.3 percent overall accuracy for per-object assessment. The mapping accuracy could be further improved given more robust segmentation algorithms and better quantity/quality of training samples. Our study shows significant promise for DCNN implementation for urban mapping and our approach can transfer to a number of other remote sensing applications.

Structural design and mechanical analysis of a new equipment for tire vulcanization

Vulcanization is a pivotal process of tire manufacturing, endowing the uncured tire with exquisite surface pattern and superior performance by converting rubber property from plasticity to elasticity. However, the defects of incomplete expansion, asymmetric structure, and vapor condensation deposition in the existing vulcanization technology inferiorly affect the uniformity and dynamic balance performance of tires. In our paper, a novel tire curing equipment, i.e., vulcanized inner mold drum (VIMD) is designed to improve the traditional vulcanization process for automobile tires. The structure design of the drum tiles, the telescopic mechanism and the transmission mechanism, and the finite element simulation analysis and reliability check of the key components are carried out. The contraction ratio is obviously increased by increasing the number of drum tiles and adopting the structural design method of arranging the link mechanisms cross-symmetrically. The ingenious design of the dual cam link mechanism enables the movement of the mechanism to proceed in an orderly manner, effectively avoids complicated controlling design. The design of self-locking structure considerably reduces the force of the links and improves the overall dimensional accuracy. The results suggest that the VIMD has excellent dimensional accuracy and structural stability. Highlights A new type equipment for tire vulcanization is proposed. The contraction ratio is obviously increased by increasing the number of drum tiles, and adopting the structural design method of arranging the link mechanisms cross-symmetrically. The ingenious design of the cylindrical cam track enables the movement of the mechanism to proceed in an orderly manner, effectively avoiding the interference of parts. The design of the dual cam link mechanism avoids complicated controlling design and effectively improves space utilization. The design of self-locking structure considerably reduces the force of the links and improves the overall dimensional accuracy.

Application of Eye Tracking in Puzzle Games for Adjunct Cognitive Markers: Pilot Observational Study in Older Adults.

BackgroundRecent studies suggest that computerized puzzle games are enjoyable, easy to play, and engage attentional, visuospatial, and executive functions. They may help mediate impairments seen in cognitive decline in addition to being an assessment tool. Eye tracking provides a quantitative and qualitative analysis of gaze, which is highly useful in understanding visual search behavior.ObjectiveThe goal of the research was to test the feasibility of eye tracking during a puzzle game and develop adjunct markers for cognitive performance using eye-tracking metrics.MethodsA desktop version of the Match-3 puzzle game with 15 difficulty levels was developed using Unity 3D (Unity Technologies). The goal of the Match-3 puzzle was to find configurations (target patterns) that could be turned into a row of 3 identical game objects (tiles) by swapping 2 adjacent tiles. Difficulty levels were created by manipulating the puzzle board size (all combinations of width and height from 4 to 8) and the number of unique tiles on the puzzle board (from 4 to 8). Each level consisted of 4 boards (ie, target patterns to match) with one target pattern each. In this study, the desktop version was presented on a laptop computer setup with eye tracking. Healthy older subjects were recruited to play a full set of 15 puzzle levels. A paper-pencil–based assessment battery was administered prior to the Match-3 game. The gaze behavior of all participants was recorded during the game. Correlation analyses were performed on eye-tracking data correcting for age to examine if gaze behavior pertains to target patterns and distractor patterns and changes with puzzle board size (set size). Additionally, correlations between cognitive performance and eye movement metrics were calculated.ResultsA total of 13 healthy older subjects (mean age 70.67 [SD 4.75] years; range 63 to 80 years) participated in this study. In total, 3 training and 12 test levels were played by the participants. Eye tracking recorded 672 fixations in total, 525 fixations on distractor patterns and 99 fixations on target patterns. Significant correlations were found between executive functions (Trail Making Test B) and number of fixations on distractor patterns (P=.01) and average fixations (P=.005).ConclusionsOverall, this study shows that eye tracking in puzzle games can act as a supplemental source of data for cognitive performance. The relationship between a paper-pencil test for executive functions and fixations confirms that both are related to the same cognitive processes. Therefore, eye movement metrics might be used as an adjunct marker for cognitive abilities like executive functions. However, further research is needed to evaluate the potential of the various eye movement metrics in combination with puzzle games as visual search and attentional marker.

Hurwitz theory of elliptic orbifolds, I

An elliptic orbifold is the quotient of an elliptic curve by a finite group. Eskin and Okounkov proved that generating functions for the number of branched covers of an elliptic curve with specified ramification are quasimodular forms for the full modular group $SL_2(\mathbb{Z})$. They later generalized this theorem to the enumeration of branched covers of a pillowcase, i.e. the quotient of an elliptic curve by the elliptic involution, proving quasi-modularity for $\Gamma_1(2)$. We generalize their work to the quotient of an elliptic curve by cyclic groups of orders $N=3$, $4$, $6$, proving quasi-modularity for level $\Gamma_1(N)$. One corollary is that certain generating functions of hexagon, square, and triangle tilings of compact surfaces are quasi-modular. These tilings enumerate lattice points in moduli spaces of flat surfaces. We analyze the asymptotic behavior as the number of tiles goes to infinity, theoretically giving an algorithm to compute the Masur-Veech volumes of moduli spaces of cubic, quartic, and sextic differentials. We also deduce that the volume is polynomial in $\pi$.