226 research outputs found
Critical natural frequency: an improved empirical effectiveness criterion in vibration stress relief of rectangle welded plates
Decreasing of natural frequency of the treated structure is the most frequently used empirical effectiveness criteria in vibration stress relief (VSR). However, dependability and reliability of this criteria is still far from sufficient. In this study, a covert negative treatment phenomenon was investigated, i.e. natural frequency of welded structures decreased after VSR but residual stress in one direction increased. Relationship between natural frequency and residual stresses was studied by mathematical deduction and finite element method. “Natural Frequency Function” and “Natural Frequency Surface (NFS)” was proposed to describe that relationship. “Critical Natural Frequency” (CNF) was proposed to depict possible situations after VSR. A quantitative natural frequency criterion for VSR effectiveness estimation was proposed
Self-Paced Multi-Task Learning
In this paper, we propose a novel multi-task learning (MTL) framework, called
Self-Paced Multi-Task Learning (SPMTL). Different from previous works treating
all tasks and instances equally when training, SPMTL attempts to jointly learn
the tasks by taking into consideration the complexities of both tasks and
instances. This is inspired by the cognitive process of human brain that often
learns from the easy to the hard. We construct a compact SPMTL formulation by
proposing a new task-oriented regularizer that can jointly prioritize the tasks
and the instances. Thus it can be interpreted as a self-paced learner for MTL.
A simple yet effective algorithm is designed for optimizing the proposed
objective function. An error bound for a simplified formulation is also
analyzed theoretically. Experimental results on toy and real-world datasets
demonstrate the effectiveness of the proposed approach, compared to the
state-of-the-art methods
Neural Polarizer: A Lightweight and Effective Backdoor Defense via Purifying Poisoned Features
Recent studies have demonstrated the susceptibility of deep neural networks
to backdoor attacks. Given a backdoored model, its prediction of a poisoned
sample with trigger will be dominated by the trigger information, though
trigger information and benign information coexist. Inspired by the mechanism
of the optical polarizer that a polarizer could pass light waves with
particular polarizations while filtering light waves with other polarizations,
we propose a novel backdoor defense method by inserting a learnable neural
polarizer into the backdoored model as an intermediate layer, in order to
purify the poisoned sample via filtering trigger information while maintaining
benign information. The neural polarizer is instantiated as one lightweight
linear transformation layer, which is learned through solving a well designed
bi-level optimization problem, based on a limited clean dataset. Compared to
other fine-tuning-based defense methods which often adjust all parameters of
the backdoored model, the proposed method only needs to learn one additional
layer, such that it is more efficient and requires less clean data. Extensive
experiments demonstrate the effectiveness and efficiency of our method in
removing backdoors across various neural network architectures and datasets,
especially in the case of very limited clean data
Microscopic and endoscopic “chopstick” technique removal of choroid plexus papilloma in the third ventricle of an infant: a case report with systematic review of literature
BackgroundChoroid plexus papilloma (CPP) is rare and even rarer in infants and young children, and it usually occurs in the ventricles. Due to the physical peculiarities of infants, tumor removal by microscopic or endoscopic surgery alone is difficult.Case PresentationA 3-month-old patient was found to have an abnormally enlarged head circumference for 7 days. Cranial magnetic resonance imaging (MRI) examination revealed a lesion in the third ventricle. The patient underwent combined microscopic and endoscopic “chopstick” technique to remove the tumor. He recovered well after the surgery. Postoperative pathological examination revealed CPP. Postoperative MRI suggested total resection of the tumor. Follow-up for 1 month showed no recurrence or distant metastasis.ConclusionsCombined microscopic and endoscopic “chopstick” technique may be a suitable approach to remove tumors in infant ventricles
Not All Metrics Are Guilty: Improving NLG Evaluation with LLM Paraphrasing
Most research about natural language generation (NLG) relies on evaluation
benchmarks with limited references for a sample, which may result in poor
correlations with human judgements. The underlying reason is that one semantic
meaning can actually be expressed in different forms, and the evaluation with a
single or few references may not accurately reflect the quality of the model's
hypotheses. To address this issue, this paper presents a novel method, named
Para-Ref, to enhance existing evaluation benchmarks by enriching the number of
references. We leverage large language models (LLMs) to paraphrase a single
reference into multiple high-quality ones in diverse expressions. Experimental
results on representative NLG tasks of machine translation, text summarization,
and image caption demonstrate that our method can effectively improve the
correlation with human evaluation for sixteen automatic evaluation metrics by
+7.82% in ratio. We release the code and data at
https://github.com/RUCAIBox/Para-Ref
A combined computational and experimental study on vibration stress relief for large welded DH36 steel tube
Vibration stress relief (VSR) is an effective and economic method for reducing residual stress in various welding components. Compared with other methods, it costs much less time and energy. In this study, finite element method (FEM) was used to assist VSR treatment of large DH36 steel welded tube by determining the 1st order vibration mode of the tube and the natural frequency of the tube in a hypothetic zero-stress state. According to the computational results, proper vibration exciting assembling and excitation strategy was selected. An effectiveness index, η, for fast and quantitative estimation of the residual stress decrease rate was proposed. η is determined by 1st order natural frequencies of the tube in three states, i.e. as-welded, VSR treated and a hypothetic zero-stress state. η in this study was 49.8 %, meeting well with the experimentally measured residual stress decrease rate, ~50 %. Thus, the validity of the effectiveness index was verified. This study provides a novel method for analysis of VSR effectiveness. In comparison, maximum residual stress was reduced by 20-57 % when traditional local post weld heat treatment (PWHT) was used. This indicates that VSR is a good stress relief method for DH36 welded structures
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