231 research outputs found
Investigation of Key Parameters for Hydraulic Optimization of an Inlet Duct Based on a Whole Waterjet Propulsion Pump System
The hydraulic performance of an inlet duct directly affects the overall performance of a waterjet propulsion system. Key parameters for the hydraulic optimization of the inlet duct are explored using the computational fluid dynamics (CFD) technology to improve the hydraulic performance of the waterjet propulsion system. In the CFD simulation and experiment, an inlet duct with different flow and geometric parameters is simulated. By comparing grid sensitivity and different turbulence models, a suitable grid size and a turbulence model are determined. The comparison between the numerical simulation and the experiment shows that the numerical results are reliable. The results of the calculation and analysis of different speed cases show that the ship speed affects the efficiency of the waterjet propulsion system. In particular, the system efficiency increases first and then decreases with an increase in the ship speed. Under the conditions of constant ship speed and rotational speed, the influence of the length and dip angle of the inlet duct on the waterjet propulsion system is investigated using a single factor method. The results show that the dip angle has an obvious effect on the hydraulic performance of the inlet duct, and an extremely small angle of inclination will lead to poor flow patterns in the inlet passage. When the length is approximately six times the inlet duct outlet diameter, and the dip angle is 30°–35°, the hydraulic performance of the waterjet propulsion pump system is satisfactory
TAE: A Semi-supervised Controllable Behavior-aware Trajectory Generator and Predictor
Trajectory generation and prediction are two interwoven tasks that play
important roles in planner evaluation and decision making for intelligent
vehicles. Most existing methods focus on one of the two and are optimized to
directly output the final generated/predicted trajectories, which only contain
limited information for critical scenario augmentation and safe planning. In
this work, we propose a novel behavior-aware Trajectory Autoencoder (TAE) that
explicitly models drivers' behavior such as aggressiveness and intention in the
latent space, using semi-supervised adversarial autoencoder and domain
knowledge in transportation. Our model addresses trajectory generation and
prediction in a unified architecture and benefits both tasks: the model can
generate diverse, controllable and realistic trajectories to enhance planner
optimization in safety-critical and long-tailed scenarios, and it can provide
prediction of critical behavior in addition to the final trajectories for
decision making. Experimental results demonstrate that our method achieves
promising performance on both trajectory generation and prediction.Comment: an updated version, change figures and references. 8 pages, robotics
conference, about trajectory augmentation and prediction for intelligent
vehicle system
Safety-driven Interactive Planning for Neural Network-based Lane Changing
Neural network-based driving planners have shown great promises in improving
task performance of autonomous driving. However, it is critical and yet very
challenging to ensure the safety of systems with neural network based
components, especially in dense and highly interactive traffic environments. In
this work, we propose a safety-driven interactive planning framework for neural
network-based lane changing. To prevent over conservative planning, we identify
the driving behavior of surrounding vehicles and assess their aggressiveness,
and then adapt the planned trajectory for the ego vehicle accordingly in an
interactive manner. The ego vehicle can proceed to change lanes if a safe
evasion trajectory exists even in the predicted worst case; otherwise, it can
stay around the current lateral position or return back to the original lane.
We quantitatively demonstrate the effectiveness of our planner design and its
advantage over baseline methods through extensive simulations with diverse and
comprehensive experimental settings, as well as in real-world scenarios
collected by an autonomous vehicle company
Safety-Assured Speculative Planning with Adaptive Prediction
Recently significant progress has been made in vehicle prediction and
planning algorithms for autonomous driving. However, it remains quite
challenging for an autonomous vehicle to plan its trajectory in complex
scenarios when it is difficult to accurately predict its surrounding vehicles'
behaviors and trajectories. In this work, to maximize performance while
ensuring safety, we propose a novel speculative planning framework based on a
prediction-planning interface that quantifies both the behavior-level and
trajectory-level uncertainties of surrounding vehicles. Our framework leverages
recent prediction algorithms that can provide one or more possible behaviors
and trajectories of the surrounding vehicles with probability estimation. It
adapts those predictions based on the latest system states and traffic
environment, and conducts planning to maximize the expected reward of the ego
vehicle by considering the probabilistic predictions of all scenarios and
ensure system safety by ruling out actions that may be unsafe in worst case. We
demonstrate the effectiveness of our approach in improving system performance
and ensuring system safety over other baseline methods, via extensive
simulations in SUMO on a challenging multi-lane highway lane-changing case
study
Evoke: Evoking Critical Thinking Abilities in LLMs via Reviewer-Author Prompt Editing
Large language models (LLMs) have made impressive progress in natural
language processing. These models rely on proper human instructions (or
prompts) to generate suitable responses. However, the potential of LLMs are not
fully harnessed by commonly-used prompting methods: many human-in-the-loop
algorithms employ ad-hoc procedures for prompt selection; while auto prompt
generation approaches are essentially searching all possible prompts randomly
and inefficiently. We propose Evoke, an automatic prompt refinement framework.
In Evoke, there are two instances of a same LLM: one as a reviewer
(LLM-Reviewer), it scores the current prompt; the other as an author
(LLM-Author), it edits the prompt by considering the edit history and the
reviewer's feedback. Such an author-reviewer feedback loop ensures that the
prompt is refined in each iteration. We further aggregate a data selection
approach to Evoke, where only the hard samples are exposed to the LLM. The hard
samples are more important because the LLM can develop deeper understanding of
the tasks out of them, while the model may already know how to solve the easier
cases. Experimental results show that Evoke significantly outperforms existing
methods. For instance, in the challenging task of logical fallacy detection,
Evoke scores above 80, while all other baseline methods struggle to reach 20
MOHO: Learning Single-view Hand-held Object Reconstruction with Multi-view Occlusion-Aware Supervision
Previous works concerning single-view hand-held object reconstruction
typically utilize supervision from 3D ground truth models, which are hard to
collect in real world. In contrast, abundant videos depicting hand-object
interactions can be accessed easily with low cost, although they only give
partial object observations with complex occlusion. In this paper, we present
MOHO to reconstruct hand-held object from a single image with multi-view
supervision from hand-object videos, tackling two predominant challenges
including object's self-occlusion and hand-induced occlusion. MOHO inputs
semantic features indicating visible object parts and geometric embeddings
provided by hand articulations as partial-to-full cues to resist object's
self-occlusion, so as to recover full shape of the object. Meanwhile, a novel
2D-3D hand-occlusion-aware training scheme following the synthetic-to-real
paradigm is proposed to release hand-induced occlusion. In the synthetic
pre-training stage, 2D-3D hand-object correlations are constructed by
supervising MOHO with rendered images to complete the hand-concealed regions of
the object in both 2D and 3D space. Subsequently, MOHO is finetuned in real
world by the mask-weighted volume rendering supervision adopting hand-object
correlations obtained during pre-training. Extensive experiments on HO3D and
DexYCB datasets demonstrate that 2D-supervised MOHO gains superior results
against 3D-supervised methods by a large margin. Codes and key assets will be
released soon
Analysis of high-speed angular ball bearing lubrication based on bi-directional fluid-solid coupling
The lubrication of angular contact ball bearings under high-speed motion conditions is particularly important to the working performance of rolling bearings. Combining the contact characteristics of fluid domain and solid domain, a lubrication calculation model for angular contact ball bearings is established based on the RNG k-ε method. The pressure and velocity characteristics of the bearing basin under the conditions of rotational speed, number of balls and lubricant parameters are analyzed, and the lubrication conditions and dynamics of the angular contact ball bearings under different working conditions are obtained. The results show that the lubricant film pressure will rise with increasing speed and viscosity of the lubricant. The number of balls affects the pressure and velocity distribution of the flow field inside the bearing but has a small effect on the values of the characteristic parameters of the bearing flow field. The established CFD model provides a new approach to study the effect of fluid flow on bearing performance in angular contact ball bearings
The Max b-HLH-LZ Can Transduce into Cells and Inhibit c-Myc Transcriptional Activities
The inhibition of the functions of c-Myc (endogenous and oncogenic) was recently shown to provide a spectacular therapeutic index in cancer mouse models, with complete tumor regression and minimal side-effects in normal tissues. This was achieved by the systemic and conditional expression of omomyc, the cDNA of a designed mutant of the b-HLH-LZ of c-Myc named Omomyc. The overall mode of action of Omomyc consists in the sequestration of Max and the concomitant competition of the Omomyc/Max complex with the endogenous c-Myc/Max heterodimer. This leads to the inhibition of the transactivation of Myc target genes involved in proliferation and metabolism. While this body of work has provided extraordinary insights to guide the future development of new cancer therapies that target c-Myc, Omomyc itself is not a therapeutic agent. In this context, we sought to exploit the use of a b-HLH-LZ to inhibit c-Myc in a cancer cell line in a more direct fashion. We demonstrate that the b-HLH-LZ domain of Max (Max*) behaves as a bona fide protein transduction domain (PTD) that can efficiently transduce across cellular membrane via through endocytosis and translocate to the nucleus. In addition, we show that the treatment of HeLa cells with Max* leads to a reduction of metabolism and proliferation rate. Accordingly, we observe a decrease of the population of HeLa cells in S phase, an accumulation in G1/G0 and the induction of apoptosis. In agreement with these phenotypic changes, we show by q-RT-PCR that the treatment of HeLa cells with Max* leads to the activation of the transcription c-Myc repressed genes as well as the repression of the expression of c-Myc activated genes. In addition to the novel discovery that the Max b-HLH-LZ is a PTD, our findings open up new avenues and strategies for the direct inhibition of c-Myc with b-HLH-LZ analogs
Evolutionary origin of genomic structural variations in domestic yaks
Yak has been subject to natural selection, human domestication and interspecific introgression during its evolution. However, genetic variants favored by each of these processes have not been distinguished previously. We constructed a graph-genome for 47 genomes of 7 cross-fertile bovine species. This allowed detection of 57,432 high-resolution structural variants (SVs) within and across the species, which were genotyped in 386 individuals. We distinguished the evolutionary origins of diverse SVs in domestic yaks by phylogenetic analyses. We further identified 334 genes overlapping with SVs in domestic yaks that bore potential signals of selection from wild yaks, plus an additional 686 genes introgressed from cattle. Nearly 90% of the domestic yaks were introgressed by cattle. Introgression of an SV spanning the KIT gene triggered the breeding of white domestic yaks. We validated a significant association of the selected stratified SVs with gene expression, which contributes to phenotypic variations. Our results highlight that SVs of different origins contribute to the phenotypic diversity of domestic yaks
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