A wideband traveling-wave circularly polarized (CP) antenna printed on a single-layer PCB for millimeter-wave (MM-Wave) applications is presented in this communication. The proposed antenna radiates ...the CP wave on the basis of the principle similar to the classical endfire-mode helical antenna. The proposed antenna is terminated with an absorber to realize traveling-wave radiation. The traveling-wave working mechanism causes the proposed antenna to have a frequency scanning function and higher stability compared with resonant antennas. Curved microstrip transmission lines are adopted as the CP radiation elements; the whole array antenna is etched on a single-layer substrate. A prototype operating at 30 GHz is fabricated and measured. The radiation beam of the proposed antenna scans from − 14.5° (28 GHz) to +22.5° (34 GHz), the axial ratios are lower than 3 dB, and the measured gains show a maximum value of 21.9 dBi at 33 GHz and a minimum value of 20.3 dBi at 28 GHz. The measured <inline-formula> <tex-math notation="LaTeX">| \text {S}_{11} | </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">| \text {S}_{21} | </tex-math></inline-formula> are lower than −10 and −16 dB, respectively, in the frequencies mentioned above.
Structured Indoor Modeling Ikehata, Satoshi; Hang Yang; Furukawa, Yasutaka
2015 IEEE International Conference on Computer Vision (ICCV),
12/2015
Conference Proceeding, Journal Article
This paper presents a novel 3D modeling framework that reconstructs an indoor scene as a structured model from panorama RGBD images. A scene geometry is represented as a graph, where nodes correspond ...to structural elements such as rooms, walls, and objects. The approach devises a structure grammar that defines how a scene graph can be manipulated. The grammar then drives a principled new reconstruction algorithm, where the grammar rules are sequentially applied to recover a structured model. The paper also proposes a new room segmentation algorithm and an offset-map reconstruction algorithm that are used in the framework and can enforce architectural shape priors far beyond existing state-of-the-art. The structured scene representation enables a variety of novel applications, ranging from indoor scene visualization, automated floorplan generation, Inverse-CAD, and more. We have tested our framework and algorithms on six synthetic and five real datasets with qualitative and quantitative evaluations. The source code and the data are available at the project website 15.
Real-time prediction by monitoring of the evolution of response variables is a central goal in predicting rock failure. A linear relation Ω̇Ω¨−1=Ctf−t has been developed to describe the time to ...failure, where Ω represents a response quantity, C is a constant and tf represents the failure time. Observations from laboratory creep failure experiments and precursors to volcanic eruptions are used to test the validity of the approach. Both cumulative and simple moving window techniques are developed to perform predictions and to illustrate the effects of data selection on the results. Laboratory creep failure experiments on granites show that the linear relation works well during the final approach to failure. For blind prediction, the simple moving window technique is preferred because it always uses the most recent data and excludes effects of early data deviating significantly from the predicted trend. When the predicted results show only small fluctuations, failure is imminent.
•A revised materials failure model is used to predict time-to-failure for eruption and creep failure•A modification to this method allows prediction with no “a priori” assumption of the rate exponent•A simple moving-window method provides the best estimate of time-to-failure
A new data-driven method that generalizes experimentally measured and/or computational generated data sets under different loading paths to build three dimensional nonlinear elastic material law with ...objectivity under arbitrary loadings using neural networks is proposed. The proposed approach is first demonstrated by exploiting the concept of representative volume element (RVE) in the principal strain and stress spaces to numerically generate the data. A computational data-training algorithm on the generalization of these principal space data to three dimensional objective isotropic material laws subjected to arbitrary deformation is given. To validate these data-driven derived material laws, large deformation and buckling analysis of nonlinear elastic solids with reference material models and engineering structure with microstructure are performed. Numerical experiments show that only seven sets of data under different stress loading paths on RVEs are required to reach reasonable accuracy. The requirements for constitutive law such as objectivity are preserved approximately. The consistent tangent modulus is also derived. The proposed approach also shows a great potential to obtain the material law between different scales in the multiscale analysis by pure data.
Rational molecular design towards high-performance photovoltaic materials with superior large-area capability is critical but still a challenge for the research field of polymer solar cells (PSCs). ...In this work, we design and synthesize a new dialkylthio-substituted conjugated polymer donor (namely PBN-S) to address this issue. PBN-S shows strong absorbance in the wavelength range of 500–700 nm and has a low-lying HOMO level of −5.48 eV, which matches that of the nonfullerene acceptor IT-4F. Optimized PSCs based on PBN-S:IT-4F demonstrate a high power conversion efficiency (PCE) of 13.10%, benefitting from the efficient charge separation, high and balanced charge mobility, ordered molecular packing and aggregation of the donor and acceptor materials in the active layer. In addition, the PCE of a PBN-S based semitransparent PSC reaches 9.83% with an average visible transmittance of 32%. What is more, remarkable PCEs of 10.21% and 10.69% were realized from spin-coated or blade-coated PSCs with an active area of 100 mm 2 , respectively, indicating the great potential of PBN-S as a donor in high-performance large-area PSC application. More importantly, the PBN-S based devices show excellent shelf-life stability, retaining over 80% of their initial PCE after 100 days storage in a nitrogen-filled glove-box or in air. These results demonstrate the promising capability of PBN-S as a donor material for future PSC applications.
Understanding the Mesozoic intraplate structural response of South China inboard of the Paleo-Pacific-South China convergent margin is a key issue in unravelling the continental tectonics of SE Asia. ...The Lianhuashan fault zone of South China represents a high-strain structure, pivotal for constraining the multi-phased intraplate deformation, strain localization, and partitioning in response to the subduction of the Paleo-Pacific plate. New data—coupled with published work—describes the geometry, kinematics, and age of this fault zone, establishing a multi-stage tectono-thermal history. The first-stage, late Jurassic shortening, involved top-to-the-W thrust-sense shear along ~NE-striking shear zones. The associated regional ~E-W shortening is interpreted to have been related to the advancing, NW-ward subduction of the Paleo-Pacific plate. The second-stage, Early Cretaceous deformation, is poorly documented in the Lianhuashan fault zone but is associated regionally with magmatism and Early Cretaceous basins, formed under ~NW-SE extension. This extension has been correlated with the rollback of the Paleo-Pacific plate. The third-stage, late Early Cretaceous ~NW-SE shortening, produced top-to-the-SE, thrust-sense shear zones. The shortening inverted the extensional basins and caused a lull in the magmatic activity. It possibly originated from the re-initiation of low-angle Paleo-Pacific subduction. The fourth-stage deformation generated the top-to-the-W Wuhua detachment, normal-sense ductile fabrics and distributed shear zones in its footwall, and widespread hanging-wall basins in the Late Cretaceous. This regional ~E-W extension has been associated with the re-initiation of slab rollback. Our work predicts episodes of slab steepening and shallowing in retreating and advancing settings. Changes in the slab geodynamics may have caused the alternating contractional and extensional episodes, as well as the flare-up, lull, and resumption of magmatism during the late Mesozoic evolution of South China.
•Structural analyses record a four-stage deformation history of the Lianhuashan fault zone.•The first stage deformation involved top-to-the-west shearing under ~E-W compression.•The second-stage deformation is related to NW-SE extension.•The third stage of NW-SE compression produced top-to-the-southeast thrusting fabrics.•The fourth-stage extension produced the detachment, ductile shear fabrics, and basins.
Because of time and space restrictions and the limited interaction capabilities of robots, it is preferable for teachers to construct a learning environment using digital reality in conjunction with ...robots. Doing so enables students to learn and interact in any scenario relevant to textbook material that can be effectively digitalized, while also promoting human-robot interaction. Here, an interactive situated learning approach was developed to improve students' learning performances. The students and robot role-played characters and immersed themselves in digital situated learning tasks and challenges. This approach included a real-time feedback mechanism to guide and evaluate the knowledge application of the students. The evaluation was performed during interactions with the robot, virtual objects, and virtual characters based on textbook context and content. The experiment was conducted during an English as a second language course for junior high school students. A total of 101 students were assigned to three groups with different approaches and their learning performance was evaluated. The experimental results indicated that students who learned with the proposed approach exhibited better learning achievement and significant positive effects in terms of learning motivation and engagement. Furthermore, interaction with physical robots improved student learning achievements significantly compared with virtual interaction. Moreover, motivation in the learning process could be enhanced using authentic objects and scenarios in the digital situated learning environment.
•Students were immersed in an interactive situated learning environment with a robot.•The robot provided challenges and immediate feedback to guide and evaluate students.•A situated interactive learning approach gave achievement, motivation, and engagement.•Learning achievement is enhanced by physical embodiment and interaction with robots.•Potential for digital situational learning improving students' learning motivation.
Abstract
Grassland degradation has emerged as a serious socio-economic and ecological problem, endangering both long-term usage and the regional biogeochemical cycle. Climate change and human ...activities are the two leading factors leading to grassland degradation. However, it is unclear what the degradation level caused by these two factors is. Using the normalized difference vegetation index (NDVI) and coefficient of variation of NDVI (CV
NDVI
), the spatial distribution features of grassland degradation or restoration were analyzed in Qilian County in the northeast of the Qinghai–Tibet Plateau. The dominant climate variables affecting NDVI variation were selected through the combination of random forest model and stepwise regression method to improve the residual trend analysis, and on this basis, twelve possible scenarios were established to evaluate the driving factors of different degraded grasslands. Finally, used the Hurst index to forecast the trend of grassland degradation or restoration. The results showed that approximately 55.0% of the grassland had been degraded between 2000 and 2019, and the area of slight degradation (NDVI
slope
> 0; CV
NDVI (slope)
> 0; NDVI
value
> 0.2) accounted for 48.6%. These regions were centered in the northwest of Qilian County. Climate and human activities had a joint impact on grassland restoration or degradation. Human activities played a leading role in grassland restoration, while climate change was primarily a driver of grassland degradation. The regions with slight degradation or re-growing (NDVI
slope
> 0; CV
NDVI (slope)
> 0), moderate degradation (NDVI
slope
< 0; CV
NDVI (slope)
> 0), and severe degradation or desertification (NDVI
slope
< 0; CV
NDVI (slope)
< 0) were dominated by the joint effects of climate and anthropogenic activity accounted for 34.3%, 3.3%, and 1.3%, respectively, of the total grassland area. Grasslands in most areas of Qilian County are forecasted to continue to degrade, including the previously degraded areas, with continuous degradation areas accounting for 54.78%. Accurately identifying the driving factors of different degraded grassland and predicting the dynamic change trend of grassland in the future is the key to understand the mechanism of grassland degradation and prevent grassland degradation. The findings offer a reference for accurately identifying the driving forces in grassland degradation, as well as providing a scientific basis for the policy-making of grassland ecological management.
Boron nitride (BN) structures are featured by their excellent thermal and chemical stability and unique electronic and optical properties. However, the lack of controlled synthesis of quality samples ...and the electrically insulating property largely prevent realizing the full potential of BN nanostructures. A comprehensive overview of the current status of the synthesis of two‐dimensional hexagonal BN sheets, three dimensional porous hexagonal BN materials and BN‐involved heterostructures is provided, highlighting the advantages of different synthetic methods. In addition, structural characterization, functionalizations and prospective applications of hexagonal BN sheets are intensively discussed. One‐dimensional BN nanoribbons and nanotubes are then discussed in terms of structure, fabrication and functionality. In particular, the existing routes in pursuit of tunable electronic and magnetic properties in various BN structures are surveyed, calling upon synergetic experimental and theoretical efforts to address the challenges for pioneering the applications of BN into functional devices. Finally, the progress in BN superstructures and novel B/N nanostructures is also briefly introduced.
Boron nitride nanostructures have attracted intense attention for their excellent properties. Controlled synthesis of quality samples and the electrically insulating property largely prevents the realization of the full potential of BN nanostructures. The current status of the synthesis and applications of two dimensional h‐BN are reviewed, as well as versatile strategies in pursuit of tunable electronic and magnetic properties in BN nanostructures.
This article presents a novel triband dual-polarized shared-aperture antenna with frequency-selective function for sub-6 GHz base station applications. The proposed antenna is composed of a ...dual-polarized square loop antenna with two parasitic loops for 2G/3G/4G (1710-2690 MHz) and a differentially fed dual-polarized planar antenna for 5G (3300-3600 and 4800-5000 MHz) base station applications. These two antennas are placed coaxially but different altitudes for saving the installation space. In order to achieve good individual performance for these two antennas in the same aperture without interference or blocking, the lower band (LB) antenna is designed as a frequency-selective surface (FSS) for the nether mid/upper bands (M/UBs) antenna. The measured results show that the proposed antenna achieves a high port isolation (>20 dB) between LB and M/UBs and a −10-dB impedance bandwidth of 50.4% (1.60-2.70 GHz), 14.9% (3.28-3.80 GHz), and 8.6% (4.75-5.18 GHz). To further validate the design concept, an antenna array composed of four LB elements and eight M/UBs elements with the corresponding spacing is fabricated and measured, which demonstrates the application of the triband shared-aperture antenna in array form.
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