539 research outputs found
Multi-Global Navigation Satellite System for Earth Observation: Recent Developments and New Progress
Full text linkThe Global Navigation Satellite System (GNSS) has made important progress in Earth observation and applications. With the successful design of the BeiDou Navigation Satellite System (BDS), four global navigation satellite systems are available worldwide, together with Galileo, GLONASS, and GPS. These systems have been widely employed in positioning, navigation, and timing (PNT). Furthermore, GNSS refraction, reflection, and scattering signals can remotely sense the Earth’s surface and atmosphere with powerful implications for environmental remote sensing. In this paper, the recent developments and new application progress of multi-GNSS in Earth observation are presented and reviewed, including the methods of BDS/GNSS for Earth observations, GNSS navigation and positioning performance (e.g., GNSS-PPP and GNSS-NRTK), GNSS ionospheric modelling and space weather monitoring, GNSS meteorology, and GNSS-reflectometry and its applications. For instance, the static Precise Point Positioning (PPP) precision of most MGEX stations was improved by 35.1%, 18.7%, and 8.7% in the east, north, and upward directions, respectively, with PPP ambiguity resolution (AR) based on factor graph optimization. A two-layer ionospheric model was constructed using IGS station data through three-dimensional ionospheric model constraints and TEC accuracy was increased by about 20–27% with the GIM model. Ten-minute water level change with centimeter-level accuracy was estimated with ground-based multiple GNSS-R data based on a weighted iterative least-squares method. Furthermore, a cyclone and its positions were detected by utilizing the GNSS-reflectometry from the space-borne Cyclone GNSS (CYGNSS) mission. Over the years, GNSS has become a dominant technology among Earth observation with powerful applications, not only for conventional positioning, navigation and timing techniques, but also for integrated remote sensing solutions, such as monitoring typhoons, river water level changes, geological geohazard warnings, low-altitude UAV navigation, etc., due to its high performance, low cost, all time and all weather
Scaling relationships between the total number of leaves and the total leaf area per culm of two dwarf bamboo species
No full textAbstract Total leaf area per plant is an important measure of the photosynthetic capacity of an individual plant that together with plant density drives the canopy leaf area index, that is, the total leaf area per unit ground area. Because the total number of leaves per plant (or per shoot) varies among conspecifics and among mixed species communities, this variation can affect the total leaf area per plant and per canopy but has been little studied. Previous studies have shown a strong linear relationship between the total leaf area per plant (or per shoot) ( A T ) and the total number of leaves per plant (or per shoot) ( N T ) on a log–log scale for several growth forms. However, little is known whether such a scaling relationship also holds true for bamboos, which are a group of Poaceae plants with great ecological and economic importance in tropical, subtropical, and warm temperate regions. To test whether the scaling relationship holds true in bamboos, two dwarf bamboo species ( Shibataea chinensis Nakai and Sasaella kongosanensis ‘Aureostriatus’) with a limited but large number of leaves per culm were examined. For the two species, the leaves from 480 and 500 culms, respectively, were sampled and A T was calculated by summing the areas of individual leaves per culm. Linear regression and correlation analyses reconfirmed that there was a significant log–log linear relationship between A T and N T for each species. For S. chinensis , the exponent of the A T versus N T scaling relationship was greater than unity, whereas that of S. kongosanensis ‘Aureostriatus’ was smaller than unity. The coefficient of variation in individual leaf area increased with increasing N T for each species. The data reconfirm that there is a strong positive power‐law relationship between A T and N T for each of the two species, which may reflect adaptations of plants in response to intra‐ and inter‐specific competition for light
Assessing the origin of some representative Archean-Paleoproterozoic porphyry Cu ± Au deposits
No full textMost known porphyry Cu ± Au deposits are exclusively associated with oxidized and sulfurrich Phanerozoic arc-related magmas, but Precambrian analogues are rare. The genesis of some
rare examples of such deposits (e.g., Tongkuangyu in Trans-North China Orogen) remains
debated, and in particular, it remains unclear as to whether similar metallogenic processes that
typify the Phanerozoic deposits also operated in the Precambrian. To resolve these issues, three
study areas were chosen to variably characterize relevant aspects of these deposits in the
context of porphyry-type metallogenies (i.e., the nature of mineralization, the redox states and
volatile element abundances of the causative magmas): (1) the ~2.1 Ga Tongkuangyu deposit
in Trans-North China Craton; (2) the ~1.88 Ga Haib porphyry Cu deposit, Southern Namibia;
and (3) representative porphyry-type Cu ± Au deposits (Côté Gold, St-Jude, and Croxall) in the
~2.7 Ga Abitibi subprovince.
At the Tongkuangyu deposit, remapping of the distribution of the host rocks, alteration, and
mineralization support a porphyry-type model where ore formation occurred at ~2.1 Ga. This
age is significantly later than the host granodiorite porphyry (~2.18 Ga) and schists (~2.5–2.2
Ga) and indicates that porphyry-type mineralization need not be linked directly to a causative
magma exposed at surface. Instead, the latter is interpreted to be represented by subjacent
porphyritic stocks and dikes.
At the Haib deposit, the host calc-alkaline plutonic rocks and mineralization are dated to ca.
1886–1881 Ma. Estimations of magmatic fO2 and S, based on zircon geochemistry, apatite µXANES spectra, and apatite S analysis, demonstrate that oxidized, sulfur-rich arc magmas
associated with porphyry Cu mineralization already existed in the late Paleoproterozoic. In addition, zircon Hf-O isotopes and whole-rock geochemistry support magmas of mantlederivation with minor crustal contributions that experienced amphibole ± plagioclase
fractionation. These features of the Haib magmas are thus similar to those for Phanerozoic
porphyry Cu deposits.
For the ~2.7 Ga TTG (tonalite-trondhjemite-granodiorite-diorite)-related porphyry-type Cu ±
Au deposits in the Abitibi subprovince, whole-rock geochemistry, zircon Hf-O isotopes, apatite
S contents, and multiple oxybarometers suggest that variable magmatic origin and fO2 for the
causative magmas. The rarity of porphyry-type Cu-Au deposits in these older settings may be
attributed to either location restriction of these favorable metallogenic conditions and/or
preservation, or exploration bias
Average life prediction of existing residential buildings based on Logistic function model
No full text
Processing and filtrating of driver fatigue characteristic parameters based on rough set
No full textSemi-Controllable Compression Schemes for Ultrasound Imaging
No full textThe application of Compressive Sampling (CS) in the medical ultrasound has been widely studied in recent years with the growing requirement of reconstructing high-quality images with smaller data size. Most of the current studies with successful CS reconstruction are mainly focusing on the mathematical applications of CS theory in ultrasound imaging. However, the randomized mechanisms in these studies are hard to be fully fulfilled in hardware. In addition, some of the studies try to discover the sparse representation of signals by ignoring a part of information rather than compressing all data. We propose a new compression scheme for fast image acquisition in ultrasound imaging using a method, which is similar in style to CS. Our scheme is based on the formulation of an inverse scattering problem (ISP), where the Born approximation have been used during its derivation. In our system, the ultrasound image are represented by a collection of hypothetical points, what can be called pixels. These points are identified by their unique spatial impulse responses relative to the elements in the transducer. The randomized linear combinations of the spatial impulse responses from the view of elements can be maintained the uniquenesses of these points, which is similar to the coding techniques in data compression. Hence, our compression scheme can be more controllable than the conventional CS, which can achieve the real-time compression of data during the acquisition stage in hardware. We employ L2-regularization to solve the ill-posed ISP rather than the L1-regularization CS since there is no any assumption of signal sparsity. In our work, we finally achieve the acceptable reconstructions by compressing the raw data to 12.5% of its original size. The results are better than 12.5% with multiplexing the received signals from 12.5% elements in the array and almost as good as 25% with multiplexing the received signals from 25% elements in the array
Food Environment around School and Students' Weight Status: A Study of Four New Jersey Low-Income Communities
Full text linkabstract: Childhood obesity has been on the rise for the past decade, and it has been hypothesized that students' food choices may be influenced by easy access to food outlets near their schools that provide unhealthful options. But the results of recent studies on the relationship between the food environment around schools and student weight status are mixed and often contradictory. Most studies have used measures of weight and height that were self-reported by students, or have relied on data from a relatively small sample of students. I examine the association between weight status among school students and the food environment surrounding their schools using professionally-measured, student-level data across the full school-age spectrum. De-identified data were obtained for over 30,000 K-12 students in 79 public schools located in four New Jersey cities. Locations of alternative food-outlets (specifically, supermarkets, convenience stores, small grocery stores, and limited-service restaurants) were obtained from commercial sources and geocoded to develop proximity measures. A simplified social-ecological framework was used to conceptualize the multi-level the association between students' BMI and school proximity to food outlets and multivariate analyses were used to estimate this relationship controlling for student- and school-level factors. Over twenty percent of the students were obese, compared to the national average at 17% (Ogden, Carroll, Kit, & Flegal, 2012). On average, students had 2.6 convenience stores, 2.9 limited-service restaurants, and 0.1 supermarkets within a quarter mile of their school. This study suggests that easy access to small grocery stores (which this study uniquely examines as a separate food outlet category) that offer healthy choices including five types of fresh vegetable, five types of fresh fruits, low-fat dairy, and lean meats is associated with lower BMI z score and lower probability of being obese for middle and high school students. This suggests that improving access to such small food outlets may be a promising area for future investigation in obesity mitigation research. Also, this study separates students of pre-schools, kindergartens and elementary schools (neighborhood schools) from that of the middle and high schools (non-neighborhood) schools because the two groups of schools have different neighborhood characteristics, as well as open-school and bussing policies that result in different levels of exposure that students have to the food outlets around the schools. The result of this study suggests that the relationship between students' weight outcomes and food environment around schools is different in the two groups of schools.Dissertation/ThesisM.S. Sustainability 201
Fine-grained Audible Video Description
Full text linkWe explore a new task for audio-visual-language modeling called fine-grained
audible video description (FAVD). It aims to provide detailed textual
descriptions for the given audible videos, including the appearance and spatial
locations of each object, the actions of moving objects, and the sounds in
videos. Existing visual-language modeling tasks often concentrate on visual
cues in videos while undervaluing the language and audio modalities. On the
other hand, FAVD requires not only audio-visual-language modeling skills but
also paragraph-level language generation abilities. We construct the first
fine-grained audible video description benchmark (FAVDBench) to facilitate this
research. For each video clip, we first provide a one-sentence summary of the
video, ie, the caption, followed by 4-6 sentences describing the visual details
and 1-2 audio-related descriptions at the end. The descriptions are provided in
both English and Chinese. We create two new metrics for this task: an
EntityScore to gauge the completeness of entities in the visual descriptions,
and an AudioScore to assess the audio descriptions. As a preliminary approach
to this task, we propose an audio-visual-language transformer that extends
existing video captioning model with an additional audio branch. We combine the
masked language modeling and auto-regressive language modeling losses to
optimize our model so that it can produce paragraph-level descriptions. We
illustrate the efficiency of our model in audio-visual-language modeling by
evaluating it against the proposed benchmark using both conventional captioning
metrics and our proposed metrics. We further put our benchmark to the test in
video generation models, demonstrating that employing fine-grained video
descriptions can create more intricate videos than using captions.Comment: accepted to CVPR 2023, Xuyang Shen, Dong Li and Jinxing Zhou
contribute equally, code link: github.com/OpenNLPLab/FAVDBench, dataset link:
www.avlbench.opennlplab.c
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