37 research outputs found
Free Vibration of Axially Functionally Graded Beam
Axially functionally graded (AFG) beam is a special kind of nonhomogeneous functionally gradient material structure, whose material properties vary continuously along the axial direction of the beam by a given distribution form. There are several numerical methods that have been used to analyze the vibration characteristics of AFG beams, but it is difficult to obtain precise solutions for AFG beams because of the variable coefficients of the governing equation. In this topic, the free vibration of AFG beam using analytical method based on the perturbation theory and Meijer G-Function are studied, respectively. First, a detailed review of the existing literatures is summarized. Then, based on the governing equation of the AFG Euler-Bernoulli beam, the detailed analytic equations are derived on basis of the perturbation theory and Meijer G-function, where the nature frequencies are demonstrated. Subsequently, the numerical results are calculated and compared, meanwhile, the analytical results are also confirmed by finite element method and the published references. The results show that the proposed two analytical methods are simple and efficient and can be used to conveniently analyze free vibration of AFG beam
AssistSR: Task-oriented Video Segment Retrieval for Personal AI Assistant
It is still a pipe dream that personal AI assistants on the phone and AR
glasses can assist our daily life in addressing our questions like ``how to
adjust the date for this watch?'' and ``how to set its heating duration? (while
pointing at an oven)''. The queries used in conventional tasks (i.e. Video
Question Answering, Video Retrieval, Moment Localization) are often factoid and
based on pure text. In contrast, we present a new task called Task-oriented
Question-driven Video Segment Retrieval (TQVSR). Each of our questions is an
image-box-text query that focuses on affordance of items in our daily life and
expects relevant answer segments to be retrieved from a corpus of instructional
video-transcript segments. To support the study of this TQVSR task, we
construct a new dataset called AssistSR. We design novel guidelines to create
high-quality samples. This dataset contains 3.2k multimodal questions on 1.6k
video segments from instructional videos on diverse daily-used items. To
address TQVSR, we develop a simple yet effective model called Dual Multimodal
Encoders (DME) that significantly outperforms several baseline methods while
still having large room for improvement in the future. Moreover, we present
detailed ablation analyses. Code and data are available at
\url{https://github.com/StanLei52/TQVSR}.Comment: 20 pages, 12 figure
PALMD regulates aortic valve calcification via altered glycolysis and NF-ÎșB-mediated inflammation
Recent genome-wide association and transcriptome-wide association studies have identified an association between the PALMD locus, encoding palmdelphin, a protein involved in myoblast differentiation, and calcific aortic valve disease (CAVD). Nevertheless, the function and underlying mechanisms of PALMD in CAVD remain unclear. We herein investigated whether and how PALMD affects the pathogenesis of CAVD using clinical samples from CAVD patients and a human valve interstitial cell (hVIC) in vitro calcification model. We showed that PALMD was upregulated in calcified regions of human aortic valves and calcified hVICs. Furthermore, silencing of PALMD reduced hVIC in vitro calcification, osteogenic differentiation, and apoptosis, whereas overexpression of PALMD had the opposite effect. RNA-Seq of PALMD-depleted hVICs revealed that silencing of PALMD reduced glycolysis and nuclear factor-ÎșB (NF-ÎșB)âmediated inflammation in hVICs and attenuated tumor necrosis factor αâinduced monocyte adhesion to hVICs. Having established the role of PALMD in hVIC glycolysis, we examined whether glycolysis itself could regulate hVIC osteogenic differentiation and inflammation. Intriguingly, the inhibition of PFKFB3-mediated glycolysis significantly attenuated osteogenic differentiation and inflammation of hVICs. However, silencing of PFKFB3 inhibited PALMD-induced hVIC inflammation, but not osteogenic differentiation. Finally, we showed that the overexpression of PALMD enhanced hVIC osteogenic differentiation and inflammation, as opposed to glycolysis, through the activation of NF-ÎșB. The present study demonstrates that the genome-wide associationâ and transcriptome-wide associationâidentified CAVD risk gene PALMD may promote CAVD development through regulation of glycolysis and NF-ÎșBâmediated inflammation. We propose that targeting PALMD-mediated glycolysis may represent a novel therapeutic strategy for treating CAVD
Coplanar Meta-Surface-Based Substrate-Integrated Waveguide Antennas with Broadband and Low Reflections for K-Band Beam Scanning
Four novel substrate-integrated waveguide (SIW) antennas are proposed, in order to obtain K-band beam scanning through the coplanar meta-surfaces of properly devised complementary split-ring resonators. More specifically, coplanar rhombus- and hexagon-shaped meta-surfaces replace the metallized via holes in the traditional SIW structure, achieving low reflection and wide bandwidth, respectively. Another trapezoid-shaped meta-surface is introduced, in order to realize good leaky-wave radiation performance with high-gain beam scanning in both rhombus- and hexagon-shaped SIW components. These designs are further extended to two different mixed types of two-row meta-surfaces, with the rhombus and hexagon structures combined in different orders to enhance the complex SIW transmission lines and antennas, which can simultaneously obtain good reflection and bandwidth with different priority, depending on the arrangement. We explain the performance differences with rhombus and hexagon meta-surfaces through the analysis of relevant equivalent circuit models and extracting the effective medium parameters, and we verify the bandwidths and radiations of four SIW antennas both numerically and experimentally. The maximum gains of the four antennas are 18.1 dBi, 17.0 dBi, 18.8 dBi and 17.1 dBi, where the corresponding relative bandwidths are 10.74%, 19.42%, 14.13% and 18.38%. The maximum simulated radiation efficiency and aperture efficiency of the proposed antennas are 91.20% and 61.12%, respectively. Our approach for generating flexible and selectable tuned electromagnetic fields from SIWs is applicable for the development of mm-Wave antennas or sensors on PCB-integrated platforms for highly directive scanning radiation
Characterization of the Dynamic Imbibition Displacement Mechanism in Tight Sandstone Reservoirs Using the NMR Technique
An experimental technique is developed to investigate the dynamic imbibition displacement mechanism in tight sandstone formations of the Yanchang group of the Ordos basin. By combining the dynamic imbibition core flooding experiments and NMR technique, the effects of the injection volume and rate on displacement efficiency are investigated. Moreover, the displacement efficiency of dynamic imbibition is compared with that of static imbibition. This study gains insights into the micromechanisms of dynamic imbibition in tight sandstone formations. It is found that the relative displacement efficiency of dynamic imbibition increases with the increase of injection volume. But the increment amplitude decreases with the increase of injection volume. With the same injection volume, the core displacement efficiency of dynamic imbibition with high permeability is obviously improved. However, the core displacement efficiency decreases rapidly with the increase of injection volume. Optimal injection volumes are recommended for tight sandstone formations with different permeabilities. With the increase of the displacement rate, the core displacement efficiency of dynamic imbibition shows a trend of first rising and then declining. There exists an optimal displacement rate in dynamic imbibition displacement, and the optimal displacement rate almost linearly increases with the increase of core permeability. The static imbibition displacement efficiency increases with the increase of soaking time, but the increment amplitude slows down obviously. The displacement efficiency of static imbibition in small pores is higher than that of dynamic imbibition. The displacement efficiency of dynamic imbibition in large pores or microcracks is significantly higher than that of static imbibition. This study provides theoretical support for the optimization and improvement of the waterflooding recovery process in tight sandstone reservoirs.Peer Reviewe
Relationship of photosynthetic carbon fixation with environmental changes in the Jiulong River estuary of the South China Sea, with special reference to the effects of solar UV radiation
National Natural Science Foundation [40876058, 40930846]; Ministry of Education of China [308015]Phytoplankton cells in estuary waters usually experience drastic changes in chemical and physical environments due to mixing of fresh and seawaters. In order to see their photosynthetic performance in such dynamic waters, we measured the photosynthetic carbon fixation by natural phytoplankton assemblages in the Jiulong River estuary of the South China Sea during April 24-26 and July 24-26 of 2008, and investigated its relationship with environmental changes in the presence or the absence of UV radiation. Phytoplankton biomass (Chl a) decreased sharply from the river-mouth to seawards (17.3-2.1 mu g L-1), with the dominant species changed from chlorophytes to diatoms. The photosynthetic rate based on Chl a at noon time under PAR-alone increased from 1.9 mu g C (mu g Chl a)(-1) L-1 in low salinity zone (SSS 20); accordingly, the carbon fixation per volume of seawater increased from 12.8 to 149 mu g C L-1 h(-1), and decreased to 14.3 mu g C L-1 h(-1). Solar UVR caused the inhibition of carbon fixation in surface water of all the investigated zones, by 39% in turbidity area and 7-10% in freshwater or mixohaline zones. In the turbidity zone, higher availability of CO2 could have enhanced the photosynthetic performance; while osmotic stress might be responsible for the higher sensitivity of phytoplankton assemblages to solar UV radiation. (C) 2011 Elsevier Ltd. All rights reserved
AssistQ: Affordance-centric Question-driven Task Completion for Egocentric Assistant
A long-standing goal of intelligent assistants such as AR glasses/robots has
been to assist users in affordance-centric real-world scenarios, such as "how
can I run the microwave for 1 minute?". However, there is still no clear task
definition and suitable benchmarks. In this paper, we define a new task called
Affordance-centric Question-driven Task Completion, where the AI assistant
should learn from instructional videos to provide step-by-step help in the
user's view. To support the task, we constructed AssistQ, a new dataset
comprising 531 question-answer samples from 100 newly filmed instructional
videos. We also developed a novel Question-to-Actions (Q2A) model to address
the AQTC task and validate it on the AssistQ dataset. The results show that our
model significantly outperforms several VQA-related baselines while still
having large room for improvement. We expect our task and dataset to advance
Egocentric AI Assistant's development. Our project page is available at:
https://showlab.github.io/assistq/.Comment: Accepted by ECCV 2022. Equal contribution: Benita Wong, Joya Chen,
You Wu; Corresponding author: Mike Zheng Sho
Nitrogen removal performance and microbial community changes in subsurface wastewater infiltration systems (SWISs) at low temperature with different bioaugmentation strategies
Poor nitrogen removal efficiency (mainly nitrate, NO3 â-N) at low temperatures strongly limits application of subsurface wastewater infiltration systems (SWISs). Seven psychrophilic strains (heterotrophic nitrifying bacteria and aerobic denitrifying bacteria) were isolated and added to SWISs to investigate the effect of embedding and direct-dosing bioaugmentation strategies on sewage treatment performance at low temperature. Both bioaugmentation strategies improved ammonium (NH4 +-N) removal efficiencies, and the embedding strategy also exhibited satisfactory NO3 â-N and total nitrogen (TN) removal efficiencies. Pyrosequencing results of the bacterial 16S rRNA gene indicated that the embedding strategy significantly decreased the indigenous soil microbial diversity (p <.05) and altered the bacterial community structure, significantly increasing the relative abundance of Clostridia, which have good nitrate-reducing activity