35 research outputs found
Theory of Linear Models for Estimating Regression Parameters with Applications to Two-Factor Studies with Unequal Sample Sizes
In this thesis we explored some topics in regression analysis. In particular, we studied what linear regression is from a matrix theory perspective, and applied analysis of variance in a setting with two factors and unbalanced sample sizes. In addition, we applied Box-Cox variable transformation as a solution when the regression model violated the normality and equal variance (also called homoscedasticity) assumption. Our main goal is to use these theories to construct models and investigate questions related to lifetime earnings of people living in America by using real data. In doing so, we used the statistical software R to perform calculation involved in variable selection models, to identify and quantify relationships between variables as well as to test hypotheses
Advancing Biomedicine with Graph Representation Learning: Recent Progress, Challenges, and Future Directions
Graph representation learning (GRL) has emerged as a pivotal field that has
contributed significantly to breakthroughs in various fields, including
biomedicine. The objective of this survey is to review the latest advancements
in GRL methods and their applications in the biomedical field. We also
highlight key challenges currently faced by GRL and outline potential
directions for future research.Comment: Accepted by 2023 IMIA Yearbook of Medical Informatic
Boosting Offline Reinforcement Learning for Autonomous Driving with Hierarchical Latent Skills
Learning-based vehicle planning is receiving increasing attention with the
emergence of diverse driving simulators and large-scale driving datasets. While
offline reinforcement learning (RL) is well suited for these safety-critical
tasks, it still struggles to plan over extended periods. In this work, we
present a skill-based framework that enhances offline RL to overcome the
long-horizon vehicle planning challenge. Specifically, we design a variational
autoencoder (VAE) to learn skills from offline demonstrations. To mitigate
posterior collapse of common VAEs, we introduce a two-branch sequence encoder
to capture both discrete options and continuous variations of the complex
driving skills. The final policy treats learned skills as actions and can be
trained by any off-the-shelf offline RL algorithms. This facilitates a shift in
focus from per-step actions to temporally extended skills, thereby enabling
long-term reasoning into the future. Extensive results on CARLA prove that our
model consistently outperforms strong baselines at both training and new
scenarios. Additional visualizations and experiments demonstrate the
interpretability and transferability of extracted skills
A molecular simulation analysis of producing monatomic carbon chains by stretching ultranarrow graphene nanoribbons
Atomistic simulations were utilized to develop fundamental insights regarding
the elongation process starting from ultranarrow graphene nanoribbons (GNRs)
and resulting in monatomic carbon chains (MACCs). There are three key findings.
First, we demonstrate that complete, elongated, and stable MACCs with fracture
strains exceeding 100% can be formed from both ultranarrow armchair and zigzag
GNRs. Second, we demonstrate that the deformation processes leading to the
MACCs have strong chirality dependence. Specifically, armchair GNRs first form
DNA-like chains, then develop into monatomic chains by passing through an
intermediate configuration in which monatomic chain sections are separated by
two-atom attachments. In contrast, zigzag GNRs form rope-ladder-like chains
through a process in which the carbon hexagons are first elongated into
rectangles; these rectangles eventually coalesce into monatomic chains through
a novel triangle-pentagon deformation structure under further tensile
deformation. Finally, we show that the width of GNRs plays an important role in
the formation of MACCs, and that the ultranarrow GNRs facilitate the formation
of full MACCs. The present work should be of considerable interest due to the
experimentally demonstrated feasibility of using narrow GNRs to fabricate novel
nanoelectronic components based upon monatomic chains of carbon atoms.Comment: 11 pages, 6 figures, Nanotechnology accepted versio
Explainable Graph Neural Network for Alzheimer's Disease And Related Dementias Risk Prediction
Alzheimer's disease and related dementias (ADRD) ranks as the sixth leading
cause of death in the US, underlining the importance of accurate ADRD risk
prediction. While recent advancement in ADRD risk prediction have primarily
relied on imaging analysis, yet not all patients undergo medical imaging before
an ADRD diagnosis. Merging machine learning with claims data can reveal
additional risk factors and uncover interconnections among diverse medical
codes. Our goal is to utilize Graph Neural Networks (GNNs) with claims data for
ADRD risk prediction. Addressing the lack of human-interpretable reasons behind
these predictions, we introduce an innovative method to evaluate relationship
importance and its influence on ADRD risk prediction, ensuring comprehensive
interpretation.
We employed Variationally Regularized Encoder-decoder Graph Neural Network
(VGNN) for estimating ADRD likelihood. We created three scenarios to assess the
model's efficiency, using Random Forest and Light Gradient Boost Machine as
baselines. We further used our relation importance method to clarify the key
relationships for ADRD risk prediction. VGNN surpassed other baseline models by
10% in the area under the receiver operating characteristic. The integration of
the GNN model and relation importance interpretation could potentially play an
essential role in providing valuable insight into factors that may contribute
to or delay ADRD progression.
Employing a GNN approach with claims data enhances ADRD risk prediction and
provides insights into the impact of interconnected medical code relationships.
This methodology not only enables ADRD risk modeling but also shows potential
for other image analysis predictions using claims data
Baichuan 2: Open Large-scale Language Models
Large language models (LLMs) have demonstrated remarkable performance on a
variety of natural language tasks based on just a few examples of natural
language instructions, reducing the need for extensive feature engineering.
However, most powerful LLMs are closed-source or limited in their capability
for languages other than English. In this technical report, we present Baichuan
2, a series of large-scale multilingual language models containing 7 billion
and 13 billion parameters, trained from scratch, on 2.6 trillion tokens.
Baichuan 2 matches or outperforms other open-source models of similar size on
public benchmarks like MMLU, CMMLU, GSM8K, and HumanEval. Furthermore, Baichuan
2 excels in vertical domains such as medicine and law. We will release all
pre-training model checkpoints to benefit the research community in better
understanding the training dynamics of Baichuan 2.Comment: Baichuan 2 technical report. Github:
https://github.com/baichuan-inc/Baichuan
DeepSearch: A Simple and Effective Blackbox Attack for Deep Neural Networks
Although deep neural networks have been very successful in
image-classification tasks, they are prone to adversarial attacks. To generate
adversarial inputs, there has emerged a wide variety of techniques, such as
black- and whitebox attacks for neural networks. In this paper, we present
DeepSearch, a novel fuzzing-based, query-efficient, blackbox attack for image
classifiers. Despite its simplicity, DeepSearch is shown to be more effective
in finding adversarial inputs than state-of-the-art blackbox approaches.
DeepSearch is additionally able to generate the most subtle adversarial inputs
in comparison to these approaches
Study on Fiber Clogging Mechanism in Sewage Pump Based on CFD–DEM Simulation
A large number of solid particles and fibrous impurities are always entrained in the fluid transported by a sewage pump, which can easily lead to the blockage of the sewage pump. In view of this, CFD–DEM simulations were conducted in this paper to reveal the fiber clogging mechanism in the sewage pump. A CFD–DEM coupling method with a fiber model was established and verified by an experimental benchmark, i.e., the rectangular flow channel. The method was then applied to a model sewage pump to, after mesh independence tests, analyze the effects of flow rate and fiber length on fiber motion and clogging. The results showed that the position of fiber retention coincides with the position of the vortex, mainly located at the inlet of the impeller, the head of the blade, the middle of the blade, and the tongue in the pump. In the case of a low flow rate, the fiber was more likely to cause blockage in the head of the blade, and in the case of a large flow rate, the fiber would wind around the tongue in the pump. At the same flow rate, long fiber was more likely to stay on the blade’s suction surface
Study on Fiber Clogging Mechanism in Sewage Pump Based on CFD–DEM Simulation
A large number of solid particles and fibrous impurities are always entrained in the fluid transported by a sewage pump, which can easily lead to the blockage of the sewage pump. In view of this, CFD–DEM simulations were conducted in this paper to reveal the fiber clogging mechanism in the sewage pump. A CFD–DEM coupling method with a fiber model was established and verified by an experimental benchmark, i.e., the rectangular flow channel. The method was then applied to a model sewage pump to, after mesh independence tests, analyze the effects of flow rate and fiber length on fiber motion and clogging. The results showed that the position of fiber retention coincides with the position of the vortex, mainly located at the inlet of the impeller, the head of the blade, the middle of the blade, and the tongue in the pump. In the case of a low flow rate, the fiber was more likely to cause blockage in the head of the blade, and in the case of a large flow rate, the fiber would wind around the tongue in the pump. At the same flow rate, long fiber was more likely to stay on the blade’s suction surface
Enhancement of ablation and ultrafast electron dynamics observation of nickel-based superalloy under double-pulse ultrashort laser irradiation
Temporally shaped femtosecond laser machining is a flexible and effective method to improve the efficiency and quality of cooling film holes. This study investigated the ablation of nickel-based superalloy by double-pulse femtosecond laser with different pulse-separations and fluences. Compared with single-pulse ablation, approximate 1.5 times enhancement of ablation area was obtained in double-pulse ablation with about 2Â ps pulse-separation. By varying the pulse-separations, the ablation area can be tuned, and at the same time, the ablation depth can be kept for little fluctuation. An improved two-temperature model and time-resolved transient reflectivity technique were used for analyzing the ablation mechanisms. We found that more energy deposition can happen from electron system to lattice system for double-pulse ablation, which makes ablation area increase. However, mechanical relaxation started at around 2Â ps, which could be suppressed by the pressure wave induced by the second sub-pulse, and finally achieved the maximum ablation area at about 2Â ps pulse-separation. Besides, laser-induced subwavelength periodic surface structures were observed under irradiation of multiple pulses. The findings may aid in understanding the ablation mechanism between nickel-based superalloy and femtosecond laser, as well as in optimizing the processing of cooling film holes