Circular Window Research Articles

Spatial Representativeness of Eddy Covariance Measurements in a Coniferous Plantation Mixed with Cropland in Southeastern China

The eddy covariance (EC) technique has been widely used as a micrometeorological tool to measure carbon, water and energy exchanges. When utilizing the EC measurements, it is critical to be aware of the long-term information on source areas. In China, large-scale forest plantations have become a dominant driver of greening and carbon sinks on the planet. However, the spatial representativeness of EC measurements on forest plantations is still not well understood. Here, an EC flux site of a coniferous plantation mixed with cropland in a subtropical monsoon climate was selected to evaluate the spatial representativeness of the two approaches. One is the fraction of target vegetation type (FTVT), which was used to detect to what degree the flux is related to the target vegetation. The other is the sensor location bias calculated from the enhanced vegetation index (EVI), which was used to detect to what spatial extent the flux can be upscaled. The results showed that the monthly footprint climatologies changed intensely throughout the year. The source area is biased toward the southeast in summer and northwest in winter. The study area was mainly a composite of coniferous plantations (70.08%) and double-cropped rice (27.83%). The double-cropped rice, with a higher seasonal variation of EVI than the coniferous plantation, was mainly distributed in the eastern areas of the study site. As a result of spatial heterogeneity and footprint variation, the FTVT was 0.89 when the wind direction was southwest; however, this reduced to 0.65 when the wind direction changed to the northeast and exhibited a single-peak seasonal variation during a year. The sensor location bias of the EVI also showed a significant monthly variation and ranged from −14.21% to 19.04% in a circular window with an increasing size from 250 to 3000 m. The overlap index between daytime and nighttime (Oday_night) can potentially be a quality flag for the GPP derived from the EC flux data. These findings demonstrate the joint effects of the monsoon climate and underlying surface heterogeneity on the spatial representativeness of the EC measurements. Our study highlights the importance of having footprint awareness in utilizing EC measurements for calibration and validation in monsoon areas.

Injection repair of CFRP using a multi-Wall carbon nanotubes-modified epoxy resin: Flexural and compression behavior

This study presented the details of multi-wall carbon nanotubes (MWCNTs)-modified resin injection repair aiming to enhance the mechanical properties, considering the flexural and compression behavior. The resin injection of epoxy resin dispersed with MWCNTs (0.1, 0.3, and 0.5 wt.%) as low viscosity resin that delaminated composite structure repair was conducted using a developed vacuum-based resin injection system at 80°C with constant injection pressure. The quasi-static indentation (QSI) method with a circular window was applied to create the barely visible impact damage (BVID) in the laminate specimen and thus obtain the delamination damage with reproducibility. The flexural strength and compression after impact (CAI) test were conducted on repaired carbon fiber reinforced laminates to assess the effect of the dispersion of the MWCNTs in the epoxy resin injection approach compared to neat epoxy resin. The mechanical test results exhibited that the recovery rate was better improved in the case of the modified resin infiltration approach in laminate composites dispersed with nanoparticles. It was attributed to their more enhanced strengthening mechanisms under effective interaction in mixed interface of fiber-matrix-MWCNTs, mainly attributing to bridge connection and stronger interfacial adhesion properties.

The use of network topology to assess connectivity of deformation bands in sandstone: A quantitative approach based on digital outcrop models

Clusters of deformation bands associated with fault damage zones modify the petrophysical properties of rocks and influence fluid migration. Many works discuss the influence of deformation bands regarding changes in porosity and permeability, but only a few address connectivity as a control of the fluid flow in porous media. We used digital outcrop models to perform a quantitative assessment of connectivity using a UAV-based system at the Melancias outcrop, Rio do Peixe Basin, Brazil. Topology determined the frequency, intensity and dimensionless intensity of deformation bands in three circular windows visually analyzed and interpreted. The geometry of the bands defines the proportion of node types, influences the distribution of I-, Y- and X-nodes, and controls the connectivity of fractures along the outcrop. Results provided by geometric and topological analyses corroborate connection per line as the more reliable connectivity indicator. Furthermore, they were crucial to defining the northeast sector as a corridor to fluid flow, whereas the other two sectors tend to be permeability barriers. We also analyzed the influence of trace lengths on the band network's overall orientation and geometric arrangement. For modeling and simulations purposes, the spatial relationships of nodes and branches help in the understand of potential hurdles to fluid migration and the variability of reservoirs and aquifers.

Unsupervised change detection in SAR images based on generalized likelihood ratio test and a two-stage morphological filter

ABSTRACT Generalized likelihood ratio test (GLRT) is an efficient method to generate difference image (DI) for change detection (CD) using synthetic aperture radar (SAR) images. GLRT is usually applied with a fixed-size moving window to the neighbourhood regions in multitemporal SAR images. The fixed window may be however not optimal for all the pixels under test. To solve disadvantages of the GLRT method, an adaptive circular window is proposed in this work. While the adaptive square window and the best fixed square window achieve an average Kappa coefficient of 83.55% and 82.12%, respectively, the adaptive circular window improves the average Kappa coefficient by 83.65% in six datasets. As another difficulty, speckle noise reduces quality of DI in SAR change detection. Three steps are considered to minimize effects of the speckle noise: (1) a two-stage morphological filter is suggested to reduce the speckle noise; (2) to generate DI, the adaptive circular window for generalized likelihood ratio test (ACWGLRT) is proposed that reduces influence of the speckle noise while preserves the edge details of multitemporal images; and (3) spatial fuzzy c-means (SFCM) is used to reduce effects of the residual speckle-noise during DI classification. The experimental results show superior performance of the proposed change detection method with respect to several competitors. The proposed method has the best Kappa coefficient and percentage correct classification (PCC) in four datasets of Ottawa, San Francisco, Farmland C, and Inland water.

Light‐Controlled Fabrication of Disordered Hyperuniform Metasurfaces

AbstractDisordered hyperuniformity (DHU) is one of the most prominent manifestations of the engineered disorder, which aims to circumvent limitations commonly related to order. Considering the k‐space, isotropic DHU is characterized by an isotropic suppression of scattering for wavenumbers k approaching zero. Thereby, stealthy DHU is a particularly strong form of DHU, where scattering is even suppressed for wavenumbers 0 < k ≤ K within a circular window of radius K. Although experimental demonstrations of DHU in optical structures exist, scalable and low‐cost fabrication methods are still rare and often lack the opportunity for in‐situ control of the k‐space. Here, a novel and facile bottom‐up approach for the fabrication of DHU metasurfaces is presented. Starting with a solution‐based deposition procedure of silver nanoparticles (AgNPs) in darkness (resulting in DHU), a more extensive way of in‐situ k‐space engineering is introduced by illuminating the growing metasurface with light (resulting in stealthy DHU). While it is shown that the wavelength of incident light allows for the in‐situ control of K, its lateral momentum k∥ defines an additional design parameter. The light‐controlled growth under maximum k∥ via surface plasmon polaritons enables the experimental confirmation of the theoretically predicted phenomenon of anisotropic stealthy DHU.

Reliability Modeling and Optimization of Circular Multi-State Sliding Time Window System with Sequential Demands

This paper proposes a new model of circular multi-state sliding time window system with sequential demands (named CMSTWS-SD). This model is an extension of the multi-state sliding window systems with considering temporal window width defined by the required completion time. For the proposed model, the system contains n multi-state elements (MEs) arranged in circular structure, and any ME can be designated as the starting point for completing the pre-specified sequential tasks. The system function depends on its capability of completing the sequential tasks within the required mission time from any possible starting points. The reliability model of the CMSTWS-SD is formulated by investigating the performance assignment schemes of each elements group starting on different MEs and adopting the extended universal generating function (UGF) technique. We suggest an approach of states aggregation to reduce the computational burden caused by the raising number of system states. Furthermore, we develop a dynamic programming algorithm for determining the optimal performance assignment scheme with minimum completion time. Since the sequence of MEs strongly affects the system reliability of considered CMSTWS-SD, we further study the optimal element sequencing problem. Numerical experiments of the system reliability evaluation and the element sequencing optimization are conducted for illustration.

A cryo-bulge apparatus for in situ weather balloon crystallization capturing during blowing by synchrotron radiation x-ray scattering.

A cryo-bulge apparatus, which can be directly installed in the synchrotron radiation x-ray scattering beamline, is designed and manufactured. Using the cryo-bulge apparatus, the crystallization of natural rubber during blowing can be captured in situ. For mechanical measurements, the rubber film is tightly clamped at the periphery of a circular window. A low temperature measurement is achieved by the presence of a large iron block, which ensures low temperature variation (<±2 °C in 1 h) during x-ray data acquisition. Since the incident x-ray beam passes through the top-most position of the rubber film, the information obtained by the current equipment is essentially under an equibiaxial deformation mode. Owing to precisely controlled internal pressure and temperature, the crystallization of rubber can be observed in situ by wide-angle x-ray scattering. The onset of crystallization is observed at a temperature T < 0 °C with an internal pressure P > 21 kPa. This suggests that the crystallization of rubber during blowing can occur under the equibiaxial deformation condition at low temperatures. The power scaling law is found to be 0.52%/kPa. The cryo-bulge apparatus is capable of clarifying the microstructural evolution of rubber during multi-dimensional deformation, which can provide guidance for the optimization of a weather balloon.

Improved Wound Healing by Naringin Associated with MMP and the VEGF Pathway.

This study aims to investigate the wound-healing effectiveness of the phenolic compound, naringin, both in vitro and in vivo. Male mice were shaved on their dorsal skin under isoflurane, a biopsy punch was made in four symmetrical circular resection windows (6 mm) to induce a wound. These excision wounds were used to study the topical effects of naringin in terms of various biochemical, molecular, and histological parameters. We observed a significant recovery in the wound area. Increased levels of MMP-2, 9, 14, TIMP-2, VEGF-A, and VEGF-R1 were induced by naringin in the HaCaT cells. The time course experiments further revealed that levels of VEGF-A and B increased within 36 h; whereas levels of VEGF-C decreased. In line with this, VEGF-R3 levels, but not VEGF-R1 and 2 levels, increased soon after stimulation; although the increase subsided after 36 h. Additionally, naringin cream upregulated wound healing in vitro. The blockage of VEGF by Bevacizumab abolished the function of naringin cream on cell migration. Histological alterations in the wounded skin were restored by naringin cream, which accelerated wound healing via upregulated expression of growth factors (VEGF-A, B, and C and VEGF-R3), and thus increased MMP-2, 9, 14 expressions.

Rose Windows in Gothic Cathedrals: A Compositional Challenge for Church Builders

Rose windows are of special significance in gothic cathedrals. These are large circular windows. They are also exquisite works of masonry. In terms of their construction, the sectioning of the circle into smaller, equal segments presented a particular challenge. The division of a circle into equal segments or the ratio between the diameter and the circumference was an old mathematical problem, which had practical consequences for architects and masons. Their answers ranged from simple to more complex solutions. Analysis has shown that the segmentation of rosettes was simpler in the early period. It later evolved into more complex segmentation, which was probably also based on anthropometric measuring systems. Perhaps the most complex segmentation of the rosette can be found in the rose windows of the Basilica of Saint Clare and the Basilica of Saint Francis in Assisi, which are presented separately.

Minimally Invasive Lateral Approach through Circular Window with a Diameter of 5 to 6 mm for Maxillary Sinus Floor Elevation with Simultaneous Implant Placement: Retrospective Study

The aims of this study were to propose a minimally invasive lateral approach technique for maxillary sinus floor elevation (MSFE) with simultaneous implant placement and to evaluate the surgical outcome and complications of this technique. This study reviewed 49 surgeries of MSFE with simultaneous implant placement (n = 83) using a minimally invasive lateral approach. A circular shape window with a diameter of 5 to 6 mm and an area of 20–30 mm2 was made on the lateral wall of the maxillary sinus. After elevation of the Schneiderian membrane, the xenograft was used for bone grafting. The MSFE was possible with a minimum-sized window in 47 of 49 cases. For the remaining 2 cases, MSFE with a minimum-sized window was failed. In one case, it was expanded to be more than 30 mm2 to repair the membrane perforation. In another case, MSFE was performed by forming two minimum-sized windows. Post-operative bleeding after MSFE occurred in one anticoagulant-treated patient. There was no failed implant during the follow-up period (mean 22 months). A minimally invasive lateral approach through a small circular window with a diameter of 5 to 6 mm is a feasible and safe technique for MSFE with simultaneous implant placement.

Development of a handheld compression optical coherence elastography probe with a disposable stress sensor.

Optical coherence elastography (OCE) is a functional extension of optical coherence tomography (OCT). OCE measures a sample's deformation under force stimuli. Compression is often used to generate the force stimuli in OCE. In this Letter, we report the development of a handheld quantitative compression OCE probe with a novel stress senor, dedicated to measuring the force. The stress sensor consists of a circular glass window and a metal ring which are connected with polyurethane spokes. This sensor is mounted on the tip of the OCT sample arm as an imaging window, so that the force applied to the sample through the window can be measured by detecting the window displacement from the OCT image. The force-displacement function was first developed through simulation on COMSOL Multiphysics and eventually calibrated experimentally. A phase-sensitive OCT technique was employed to measure both the window displacement and the sample deformation. The performance of an OCE probe with this stress sensor was evaluated on a two-layer phantom. The results show that it is extremely capable of measuring the sample Young's modulus. Finally, we successfully measured the elasticity of the human fingertip, indicating a good potential of this OCE probe for in vivo elastogram measurement on human skin.

Illumination distribution and daylight glare evaluation within different windows for comfortable lighting

Although the application of natural light illumination has great benefits in energy saving and physical and mental health of occupants, it also potentially causes glare which affects people's visual comfort. The illumination distribution and daylight glare with different windows were investigated in the paper. For illumination distribution, the results show that as the height of the windowsill increases from 0.8 m to1.6 m, the maximum illumination decreasing by 2148 lx, the minimum illumination gradually increased and changed less, increasing by 93 lx. Circular window results in the smallest indoor illumination, the maximum and minimum of the indoor illumination show little difference for the other four window shapes with the same windowsill heights and window area. And the indoor illumination increases gradually with the glass transmittance increasing. For daylight glare evaluation, the results show that the glare gradually decreases as the height of the windowsill increases from the ground. The rectangular window produces the strongest glare, the circular and square windows produce almost the same glare, less than the rectangle window. The ribbon and arched windows produce similar glare with the minimal extent under the same windowsill height and window area. Moreover, the greater the glass transmittance, the worse the glare is.

A level set model by regularizing local fitting energy and penalty energy term for image segmentation

A novel level set model is proposed by regularizing local fitting energy to segment the intensity inhomogeneous images. In proposed model, local image fitting energy information is incorporated with penalty energy function. To segment intensity inhomogeneous images, a circular window filter is used to identify homogeneous regions. In addition, local information of homogeneous regions is constructed in form of local fitting function. A new double well potential function is formulated to regularize the contour curve and is used a penalty energy term which is added with local fitting functional in order to formulate multi-scale energy function. The experimental results show the robustness of proposed method compared to other level set models and deep learning based level set model. The comparative study of Jaccard similarity index (JSI) values and segmentation accuracy also validate the preciseness of the proposed model. Further, the proposed model yields better segmentation results compared to the other state-of-the-art models in terms of higher precision and recall values and lesser computational time. In addition, the proposed model is computationally efficient and robust to noise as well as contour initialization.

Wideband Output Brewster Window for Terahertz TWT Amplifiers Application

A wideband terahertz (THz) output network consisting of a pyramidal horn and a diamond Brewster window has been developed for 0.7-1.0-THz traveling-wave tube (TWT) amplifier and is measured at 0.325-0.5 THz owing to the limitation of the measurement facility. A pyramidal horn is designed to convert the waveguide mode into a high-purity quasi-plane polarized mode to meet the demand of the Brewster window. A diamond Brewster window plate with low THz transmission loss is fabricated via chemical vapor deposition (CVD). The plate is directly placed on the pyramidal horn with a Brewster angle. A circular window plate supporter is intended to balance the stress distribution during diamond-metal brazing. The measurement shows transmission coefficient is better than 0.85 within a wide bandwidth of 0.325-0.5 THz. This letter provides a practical way for a single diamond window structure for THz TWT amplifiers.

Multiobjective fuzzy clustering with multiple spatial information for Noisy color image segmentation

Clustering method is a widely used and effective technique in color image segmentation. In general, traditional clustering-based image segmentation algorithms consider only one objective function and the segmentation performance is easily influenced by the noise in the image. Therefore, utilizing many clustering criteria and the neighborhood statistic information of pixels are more effective to improve the segmentation performance. In this paper, we put forward a multiobjective fuzzy clustering algorithm with multiple spatial information (MFCMSI) for noisy color image segmentation. Firstly, two conflicting fitness functions including the local spatial information with a circular neighborhood window and the non-local spatial information with circular search and similarity windows are designed to improve the noise-resistant ability and segmentation performance. In order to optimize these two fitness functions, the variable-length and cluster-center-based encoding strategy and some efficient evolutionary operations are utilized in each generation. Finally, a cluster validity index with multiple spatial information is constructed to select the best solution from the final non-dominated solution set of the last generation. Aiming to improve the robustness of MFCMSI, the ensemble strategy is introduced into MFCMSI and an ensemble version of MFCMSI is presented. Experimental results show that MFCMSI and its ensemble version behave well in evolving the number of segments and obtaining the satisfactory segmentation performance.

Effect of window configurations on its convective heat transfer rate

ASHRAE Standard 90.1 provides a useful guideline for the Window-to-Wall Ratio (WWR), stating that “the total vertical fenestration area shall be less than 40% of the gross wall area” However, different window configurations with the same WWR can perform thermally differently. In this paper, the effect of window configurations on the convective heat transfer rate of a window and downdraft velocity is investigated numerically at different Rayleigh numbers ranging from 1.7 × 106 to 1.7 × 1011. Parameters investigated in this study include window shape, heater location, and heater temperature. A convective heat transfer rate of each of the window models is evaluated using high-resolution 3-D steady Reynolds Averaged Navier-Stokes (RANS) based computational fluid dynamics (CFD) simulations. The heater and the window are modeled as isothermal plane boundaries, where the window possesses a cold temperature, and the natural convective heater is hotter than room temperature. The sensitivity of the window Nusselt number and downdraft velocity of the windows have been examined. The thermal performance ranking, from higher to lower, is horizontal rectangular, square, circular, and vertical rectangular window configuration, respectively. This implies that proper window geometry configuration selection can be used as one of the passive strategies for saving energy in buildings.

Reliability analysis of seismic attribute in the detection of fault-karst

In the Tarim Basin, various irregular fractured-vuggy reservoirs have developed along with the main faults. These reservoirs are geologically defined as carbonate fault karst. In the past few years, seismic attributes have been widely used for the identification and evaluation of fault karst. However, there has been less reliability analysis regarding their usage. Imaging using the theoretical fault-karst velocity model can reflect the shapes and distributions of fractures and vugs, whereas imaging using the background velocity can simulate seismic data in real cases. We have adopted an approach based on typical fault-karst theoretical forward modeling to evaluate the reliability of seismic attributes in practical applications. First, we extract various attributes from the images using the theoretical velocity and the background velocity using similarity estimation between them to optimize the sensitive attributes. The analysis result indicates that the instantaneous phase, variance, amplitude gradient, coherence, and texture entropy are more suitable to characterize the anomalies of fractures and vugs with prediction accuracy of 71.7%. Because fracture orientation and density are the key parameters for quantifying the differences between the two images, taking coherence as an example, we extract the fracture traces through circular scanlines and circular windows based on the optimized attributes. The coincidence rate between the predicted fracture density and the known model reaches 83%, and that between the predicted fracture orientation and the known model is greater than 95%. With this remarkable coincidence, we can conclude that optimized seismic attributes are reliable for characterizing fractured-vuggy reservoirs.

Biomechanical Analysis of Window Configuration of Femur under Different Loading Conditions

Background: In surgeries, when making a window in the bone cortex is necessary, a circular window is usually recommended. A review of the literature did not yield any positive evidence indicating the preference for the circular shape under bending and compression loading. Objectives: In this study, we examined this issue using two methods, including software analysis and performing load tests in laboratory. Methods: Windows of different shapes with the same area were made in 40 femoral bones of the same-weight New Zealand rabbits, and then they were put under bending and compression force by a hydraulic device in the laboratory to measure the force required to fracture the bone by a computer. Simultaneously, ANSYS® software was used to simulate the test by the Biomechanics Research Team of the University of Technology. Results: According to the results obtained from software analysis and simulation, under compression and bending loading conditions, the mean fracture force in a trapezoidal shape was more than that in circular, square, and triangular shapes. These results were also confirmed in the experiments. Conclusion: Based on the results, no significant difference was observed between these shapes under the bending force. Moreover, under compression loading, no significant difference was found between trapezoidal and circular shapes.

Predictive modeling of bedrock outcrops and associated shallow soil in upland glaciated landscapes

Identifying the areal extent of bedrock outcrops and shallow soils has important implications for understanding spatial patterns in vegetation composition and productivity, stream chemistry gradients, and hydrologic and soil properties of landscapes. Manual methods of delineating bedrock outcrops and associated shallow soils are still commonly employed, but they are expensive to implement over broad areas and often limited by representation of polygon units. Few studies have automated the delineation of bedrock outcrops. These focused on delineation approaches in landscapes with rapidly eroding hillslopes and sparse vegetation. The objectives of this study were to assess the accuracy of visually interpreting high-resolution relief maps for locating bedrock outcrops and associated shallow soil (BOSS) <50 cm deep in a heavily forested landscape, to use visually interpreted point locations to train predictive models, and to compare predictions with manually delineated polygons in upland glaciated landscapes. Visual interpretation of Lidar-derived 1 m shaded relief maps at Hubbard Brook Experimental Forest (HBEF), USA resulted in a 79% accuracy of interpreting deep soil locations and 84% accuracy in distinguishing BOSS. We explored four probabilistic classifications of BOSS using multiple Lidar-derived topographic metrics as predictive variables. All four methods identified similar predictors for BOSS, including slope and topographic position indices with a 15, 100 and 200 m circular analysis window, respectively. Although all classifiers yielded similar results with little difference in interpretation, a generalized additive model had slightly higher accuracy predicting BOSS presence, yielding 85% overall accuracy using independent validation data across the primary study area, and 86% overall accuracy in a second validation area.

Technical Report: Repeatability of Contrast Sensitivity Test in Children.

This study aimed to evaluate the repeatability and normal range of the contrast sensitivity function measured using the Topcon CC-100 instrument, in children aged between 4 and 9 years, for use as a diagnostic tool. Contrast sensitivity was measured in 25 children, 11 boys and 14 girls, with normal or corrected-to-normal visual acuity, normal binocular function, and stereopsis. Two measurements were performed, 3 months apart, with a Topcon CC-100 device using achromatic sinusoidal gratings of 1.5, 3, 6, 12, and 18 cycles per degree (cpd) with random orientation in a circular window with sharp edges. The normal range in the first visit is wider than in the second. Coefficients of variation are better for the middle-range spatial frequencies (6.6 and 7.8% at 3 and 6 cpd, respectively) and worst at 18 cpd (18.2%), with intermediate values at 1.5 cpd (11.3%) and 12 cpd (13.7%), and better for older than for younger children. No significant sex differences were found (P > .05, Mann-Whitney U test). Repeatability measured by the coefficient of variation is better for the middle frequency range (3 and 6 cpd) than for low (1.5 cpd) and high frequencies (12 and 18 cpd). The variability of the differences between the first and second measurements suggests that the participants were not able to maintain a stable response criterion. The test seems to be subject to a learning effect, and the standard normality range may not be adequate for children.