228 research outputs found
Damage response of hull structure subjected to contact underwater explosion
A high-pressure shock wave was produced during a process near-field underwater explosion, which led to serious damage into structures. A Smooth Particle Hydrodynamic (SPH) method is suitable for solving problems with large deformations. Hence, it is used to investigate pressure characteristics and dynamic response of hull structures subjected to near-field underwater explosion. Effect of free surface was taken into consideration. Propagation of shock wave in multi medium and its dynamic response to hull structures were analyzed
The flow field simulation on Dianchi Lake
AbstractAccording to the hydro-dynamics models‘principle and the comprehensive roughness of the wetland determined by flume experiment, as well as some available information about Dianchi Lake, such as ecological environment construction plan, previous studies, wetland plants and the change of Lake water conditions, a vertical-averaged 2-D hydrodynamic model is established. The model is applied to simulate the flow field under 3 situations: present lake water, lake waters after breakwater removal and wetland build. Wetland plants and the change of the water boundary conditions influencing on the flow field are analyzed. The simulation results show that, removal of the breakwater to expand water have a faint effect on Dianchi Lake, however, it changes the boundary conditions and the part direction of wind-driven current, thus the part flow field is addition. The average flow velocity increases from 0.73 cm/s to 1.18 cm/s in the area between Fubao and Xishan in the north of Dianchi, increasing by 61.6%. The average flow velocity increases from 0.34 cm/s to 0.57 cm/s, increasing by 67.6%, in Kun-yang in the portion area of the north of Dianchi. In rest areas, the average flow velocity changes a little from 1.22 cm/s to 1.32 cm/s, increasing by 8.2%. The effect of ecological wetland on flow field of Dianchi lake mainly happens in the wetland areas, however, the effect on rest areas is limit. The average flow velocity of wetland is from 0.43 cm/s to 0.14 cm/s, deceasing by 67.4%. The velocity of the rest areas is basically constant, from 1.27 cm/s to 1.21 cm/s, deceasing by 4.7%. The research results play a significant role on restoring and constructing ecological environment of Dianchi Lake
Induction of Reproductive Diapause in \u3ci\u3eHabrobracon hebetor\u3c/i\u3e (Hymenoptera: Braconidae) When Reared at Different Photoperiods at Low Temperatures
Development of the parasitoid Habrobracon hebetor (Say) (Hymenoptera: Braconidae) at low temperatures was determined to identify rearing conditions that might result in adults that were in reproductive diapause. Diapausing adults would be expected to survive cold storage longer than nondiapausing adults for use in biological control programs. Only a few eggs were found in the ovaries when H. hebetor females were reared during the immature stages at 17.5 and 20°C with a 16-h photoperiod, and the ovaries were poorly developed and contained no eggs when females were reared with a 10-h photoperiod in these low temperatures. Rearing H. hebetor at 17.5 and 20°C did not result in diapause of immature stages, but did appear to result in possible adult reproductive diapause when the immature stages were reared with a 10-h photoperiod. Females reared during the immature stages at 17.5°C with a 10-h photoperiod lived longer and took longer to lay their first eggs and to lay 50% of their eggs than those females reared at 17.5°C with a 16-h photoperiod. Females reared during the immature stages at 20°C with a 10-h photoperiod took longer to lay their first eggs and to lay 50% of their eggs, and they had a lower respiration rate, than those females reared at 20°C with a 16-h photoperiod. Females that were reared in conditions that appeared to induce reproductive diapause resumed oviposition and their respiration rate increased soon after being transferred to a higher temperature (27.5°C). Thus, females reared at a 10-h photoperiod at 17.5 and 20°C appear to enter reproductive diapause
A New Algorithm to Classify the Homogeneity of ERS-2 Wave Mode SAR Imagette
A new classification parameter is developed using 1535 ERS-2 wave mode synthetic aperture radar (SAR) test imagettes to better differentiate homogeneous and inhomogeneous imagettes. The comparison between the new parameter (Min) and the previous one (Inhomo) (Schulz-Stellenfleth and Lehner, 2004) was done under varied threshold values of Inhomo. It is concluded that the performance of ‘Min’ is much better than ‘Inhomo’ when applying to the 1535 test imagettes. Furthermore, both Min and Inhomo are applied to nearly 1 million imagettes collected for the period from 1 September 1998 to 30 November 2000. The comparisons of the global inhomogeneous distribution between ‘Min’ and ‘Inhomo’ reveal that both the areas and percentage of inhomogeneity calculated by ‘Min’ are larger than that calculated by ‘Inhomo’. By analyzing the low wind speed distribution of HOAPS data, we found that low wind speed over the ocean is one of the key reasons for the inhomogeneity of SAR imagettes
VaQuitA: Enhancing Alignment in LLM-Assisted Video Understanding
Recent advancements in language-model-based video understanding have been
progressing at a remarkable pace, spurred by the introduction of Large Language
Models (LLMs). However, the focus of prior research has been predominantly on
devising a projection layer that maps video features to tokens, an approach
that is both rudimentary and inefficient. In our study, we introduce a
cutting-edge framework, VaQuitA, designed to refine the synergy between video
and textual information. At the data level, instead of sampling frames
uniformly, we implement a sampling method guided by CLIP-score rankings, which
enables a more aligned selection of frames with the given question. At the
feature level, we integrate a trainable Video Perceiver alongside a
Visual-Query Transformer (abbreviated as VQ-Former), which bolsters the
interplay between the input question and the video features. We also discover
that incorporating a simple prompt, "Please be critical", into the LLM input
can substantially enhance its video comprehension capabilities. Our
experimental results indicate that VaQuitA consistently sets a new benchmark
for zero-shot video question-answering tasks and is adept at producing
high-quality, multi-turn video dialogues with users
Object-fabrication Targeted Attack for Object Detection
Recent researches show that the deep learning based object detection is
vulnerable to adversarial examples. Generally, the adversarial attack for
object detection contains targeted attack and untargeted attack. According to
our detailed investigations, the research on the former is relatively fewer
than the latter and all the existing methods for the targeted attack follow the
same mode, i.e., the object-mislabeling mode that misleads detectors to
mislabel the detected object as a specific wrong label. However, this mode has
limited attack success rate, universal and generalization performances. In this
paper, we propose a new object-fabrication targeted attack mode which can
mislead detectors to `fabricate' extra false objects with specific target
labels. Furthermore, we design a dual attention based targeted feature space
attack method to implement the proposed targeted attack mode. The attack
performances of the proposed mode and method are evaluated on MS COCO and
BDD100K datasets using FasterRCNN and YOLOv5. Evaluation results demonstrate
that, the proposed object-fabrication targeted attack mode and the
corresponding targeted feature space attack method show significant
improvements in terms of image-specific attack, universal performance and
generalization capability, compared with the previous targeted attack for
object detection. Code will be made available
Effects of metastasis-associated in colon cancer 1 inhibition by small hairpin RNA on ovarian carcinoma OVCAR-3 cells
<p>Abstract</p> <p>Background</p> <p>Metastasis-associated in colon cancer 1 (MACC1) is demonstrated to be up-regulated in several types of cancer, and can serve as biomarker for cancer invasion and metastasis. To investigate the relations between MACC1 and biological processes of ovarian cancer, MACC1 specific small hairpin RNA (shRNA) expression plasmids were used to investigate the effects of MACC1 inhibition on ovarian carcinoma OVCAR-3 cells.</p> <p>Methods</p> <p>Expressions of MACC1 were detected in different ovarian tissues by immunohistochemistry. MACC1 specific shRNA expression plasmids were constructed and transfected into OVCAR-3 cells. Then, expressions of MACC1 were examined by reverse transcription polymerase chain reaction (RT-PCR) and Western blot. Cell proliferation was observed by MTT and monoplast colony formation assay. Flow cytometry and TUNEL assay were used to measure cell apoptosis. Cell migration was assessed by wound healing and transwell migration assay. Matrigel invasion and xenograft model assay were performed to analyze the potential of cell invasion. Activities of Met, MEK1/2, ERK1/2, Akt, cyclinD1, caspase3 and MMP2 protein were measured by Western blot.</p> <p>Results</p> <p>Overexpressions of MACC1 were detected in ovarian cancer tissues. Expression of MACC1 in OVCAR-3 cells was significantly down-regulated by MACC1 specific small hairpin RNA. In OVCAR-3 cells, down-regulation of MACC1 resulted in significant inhibition of cell proliferation, migration and invasion, meanwhile obvious enhancement of apoptosis. As a consequence of MACC1 knockdown, expressions of Met, p-MEK1/2, p-ERK1/2, cyclinD1 and MMP2 protein decreased, level of cleaved capase3 was increased.</p> <p>Conclusions</p> <p>RNA interference (RNAi) against MACC1 could serve as a promising intervention strategy for gene therapy of ovarian carcinoma, and the antitumor effects of MACC1 knockdown might involve in the inhibition of HGF/Met and MEK/ERK pathways.</p
Rethinking Sensors Modeling: Hierarchical Information Enhanced Traffic Forecasting
With the acceleration of urbanization, traffic forecasting has become an
essential role in smart city construction. In the context of spatio-temporal
prediction, the key lies in how to model the dependencies of sensors. However,
existing works basically only consider the micro relationships between sensors,
where the sensors are treated equally, and their macroscopic dependencies are
neglected. In this paper, we argue to rethink the sensor's dependency modeling
from two hierarchies: regional and global perspectives. Particularly, we merge
original sensors with high intra-region correlation as a region node to
preserve the inter-region dependency. Then, we generate representative and
common spatio-temporal patterns as global nodes to reflect a global dependency
between sensors and provide auxiliary information for spatio-temporal
dependency learning. In pursuit of the generality and reality of node
representations, we incorporate a Meta GCN to calibrate the regional and global
nodes in the physical data space. Furthermore, we devise the cross-hierarchy
graph convolution to propagate information from different hierarchies. In a
nutshell, we propose a Hierarchical Information Enhanced Spatio-Temporal
prediction method, HIEST, to create and utilize the regional dependency and
common spatio-temporal patterns. Extensive experiments have verified the
leading performance of our HIEST against state-of-the-art baselines. We
publicize the code to ease reproducibility.Comment: 9 pages, accepted by CIKM'2
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