3,917 results on '"Nguyen Tung"'
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2. Controlling Output Power to Enhance the Investment Efficiency of Wind Farms by Maximizing the Capacity of Transmission Transformers and Integrating Energy Storage Systems
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Truong Viet Anh, Nguyen Tung Linh, and Dinh Ngoc Sang
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wind power optimization ,electricity market ,energy storage systems ,dynamic transformer ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Technology (General) ,T1-995 ,Information technology ,T58.5-58.64 - Abstract
This study addresses inherent challenges stemming from uncertainty associated with the integration of wind energy into the electricity market. A novel approach is proposed to leverage the capabilities of dynamic transformers to optimize the utilization of uncertain wind power output, thereby enhancing financial investment efficiency for wind power stakeholders. The flexible combination of wind turbines (WTB), transmission transformers (TTS), and Energy Storage Systems (ESS) can actively reserve or provision electricity. Electricity generation control is based on optimal analysis results using linear integer programming algorithms that consider temperature fluctuations, lifespan of transformers, and electricity market prices. Maximizing the dynamic transformer's efficiency as proposed and optimizing revenue and costs from the fluctuating wind power output significantly improves financial performance metrics when investing in wind farm projects. Financial figures highlighted in the paper emphasize notable benefits, particularly for wind farm expansion projects. The potential return on investment ratio is expected to increase up to 5.64 times compared to conventional wind farm investment scenarios, with an improvement to increase from 4.4% to 24.8.
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- 2024
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3. Optimizing the Location and Capacity of DGs and SOPs in Distribution Networks using an Improved Artificial Bee Colony Algorithm
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Nguyen Tung Linh and Pham Vu Long
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Artificial Bee Colony ,Cauchy algorithm ,Grenade Explosion Method ,Reconfiguration distribution network ,Soft Open Point ,optimaziton power loss reduction ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Technology (General) ,T1-995 ,Information technology ,T58.5-58.64 - Abstract
This study proposes an improved method of the Artificial Bee Colony (ABC) algorithm for the distribution network in scenarios where distributed generation sources and Soft Open Points (SOPs) are connected to optimize power control. Improvement is achieved by integrating the ABC algorithm with the Grenade Explosion Method and Cauchy to accelerate the ABC algorithm's speed. The objective function is considered to reduce power losses over a day. The proposed method was tested on the IEEE-33 bus test system under various scenarios: Case 1 with 3 DGs installed, Case 2 with 3 DGs and 1 SOP simultaneously installed in the distribution network, and Case 3 having the same configuration as Case 2 but operating for 24 hours. In addition to reducing power losses, the voltage at the nodes in the distribution grid was also improved, maintained above 0.95 pu and close to 1 pu. Case 3 showed that integrating a Wind Turbine (WT), two Photovoltaic (PV) generators, and one SOP during operation resulted in the lowest energy losses, smaller than a system with only one WT and two PVs, and significantly lower than the baseline system without any DGs and SOPs. Therefore, employing SOPs in a distribution network with integrated DGs can offer significant benefits in reducing energy losses.
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- 2024
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4. A Novel Combination of Genetic Algorithm, Particle Swarm Optimization, and Teaching-Learning-Based Optimization for Distribution Network Reconfiguration in Case of Faults
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Nguyen Tung Linh
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genetic algorithm ,particle swarm optimization ,teaching-learning-based optimization ,reconfiguration distribution network ,power loss reduction ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Technology (General) ,T1-995 ,Information technology ,T58.5-58.64 - Abstract
Reconfiguring distribution networks involves modifying their topological structure by managing switch states. This process is crucial in smart grids, as it can isolate faults, minimize power loss, and enhance system stability. However, in existing research, the reconfiguration task is often treated as a problem of either single- or multi-objective optimization and frequently overlooks the issue's multimodality. As a result, the solutions derived may be inadequate or unfeasible when facing environmental changes. In this study, the objective function of minimizing power loss considers the case of faults in the distribution grid. Coordinating the initial population division of the Genetic Algorithm (GA) with the Particle Swarm Optimization (PSO) and the Teaching and Learning-Based Optimization (TLBO) algorithms accelerates the process of finding the optimal solution, resulting in faster and more reliable results. The proposed method was tested on the IEEE-33 bus test system and was compared with other methods, demonstrating reliable results and superior efficiency.
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- 2024
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5. A Novel Solution Method for the Distribution Network Reconfiguration Problem based on an Objective Function and considering the Cost of Electricity Transmission
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Nguyen Tung Linh and Pham Vu Long
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simulation annealing algorithm ,genetic algorithms ,distribution network reconfiguration ,transmission system usage ,transmission cost allocation ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Technology (General) ,T1-995 ,Information technology ,T58.5-58.64 - Abstract
The problem of distribution reconfiguration is an important issue in the optimal operation of distribution networks. Nowadays, with the diverse development of renewable energy sources, the uncertainty of the load becomes more complex, and the need for competitive retail electricity markets is more evident. This paper presents an optimal solution to this problem, utilizing the global advantage of the simulated annealing algorithm, improving the time parameter, and combining it with the rapid mutation ability of the genetic algorithm. Simultaneously, the Zbus, EBE, and PS models were integrated to optimize the costs, considering transmission costs under constraints related to taxes and economic indicators when connected to the distribution grid. The proposed method was simulated and tested on the IEEE 33-node standard power grid with three different scenarios. The simulation results showed that the proposed method provides optimal results, which can be applied to calculate the optimal operation of the distribution grid when participating in retail electricity markets.
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- 2023
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6. An efficient and green synthesis of 2-phenylquinazolin-4(3H)-ones via t-BuONa-mediated oxidative condensation of 2-aminobenzamides and benzyl alcohols under solvent- and transition metal-free conditions
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Nguyen Vy T. B., Tran Dat P., Nguyen Tung T., Nguyen Khoa D., and Le Ha V.
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2-phenylquinazolin-4(3h)-one ,benzyl alcohol ,green conditions ,oxidative coupling ,Chemistry ,QD1-999 - Abstract
Quinazolinone synthesis usually requires employing sensitive substrates, hazardous solvents, large excess oxidants, and expensive catalysts. In this study, an efficient and environmentally benign pathway was developed to synthesize 2-phenylquinazolin-4(3H)-one via oxidative coupling between commercially available and stable chemicals, including 2-aminobenzamide and benzyl alcohol without toxic oxidizing agents and transition-metal catalysts. A high yield of the desired product (up to 84%) was obtained at 120°C for 24 h in the presence of oxygen as a green oxidant and t-BuONa as a base. Importantly, the study scope was expanded toward successfully producing various 2-phenylquinazolin-4(3H)-one derivatives in moderate-to-good yields. Furthermore, control experiments proposed that the conversion involved the initial partial oxidation of benzyl alcohol to the benzaldehyde intermediate under basic conditions, followed by the condensation, intramolecular nucleophilic addition, and oxidative dehydrogenation to 2-phenylquinazolin-4(3H)-one.
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- 2023
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7. Rapidly Determine the Maximum Power Point in the Parallel Configuration of the Photovoltaic System
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Bui Van Hien, Truong Viet Anh, Nguyen Tung Linh, and Pham Quoc Khanh
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modified P&O algorithm ,parallel PV configuration ,fill factor ,MPPT ,Chemical technology ,TP1-1185 - Abstract
The maximum power point tracking (MPPT) solutions improve power generation efficiency, quickly stabilizing the output waveform of photovoltaic (PV) systems under variable operating conditions. Along with new algorithms, improved and adjusted methods to exploit energy from PV systems are increasingly being researched and proposed. However, the proposed solutions based on the traditional algorithms and their improvements have poor performance, while the advanced algorithms or hybrid methods bring high performance but need to be simplified, and the response speed is higher. Moreover, a suitable PV configuration makes choosing a simple but highly efficient algorithm, especially in low-power PV system applications such as rooftop solar power, traffic lights, and moving vehicles…where the number of PV panels is insufficient to implement flexible configurations. This paper proposes a modified version of the Perturb and Observe (MPO) algorithm to improve MPPT performance and increase convergence speed in the parallel structure of PV panels. The Short-Circuit Current (Isc) and Open-Circuit Voltage (Voc) are calculated directly at specific operating conditions to quickly determine the potential maximum power point (MPP) that will reduce power interruptions and increase power generation efficiency compared to periodic updates. Therefore, the proposed solution converges faster, with higher efficiency, and the output signal in static and dynamic MPPT situations is more stable. The results show that the highest efficiency in simulation and experiment is 99.99% and 99.93%, respectively, while the convergence speed is 0.01 s and 0.03 s, respectively. They are better than the traditional Perturb and Observe (P&O) algorithm, the Variable Step Size Perturb and Observe (VSSP&O) method, and the Particle Swarm Optimization (PSO) technique under the same operating conditions. In addition, its performance and convergence speed are also compared with the latest introduced algorithms. The results show that it is valuable and reliable for parallel PV configuration.
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- 2023
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8. Defect Prediction with Content-based Features
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Pham, Hung Viet and Nguyen, Tung Thanh
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Computer Science - Software Engineering ,Computer Science - Computation and Language ,Computer Science - Machine Learning - Abstract
Traditional defect prediction approaches often use metrics that measure the complexity of the design or implementing code of a software system, such as the number of lines of code in a source file. In this paper, we explore a different approach based on content of source code. Our key assumption is that source code of a software system contains information about its technical aspects and those aspects might have different levels of defect-proneness. Thus, content-based features such as words, topics, data types, and package names extracted from a source code file could be used to predict its defects. We have performed an extensive empirical evaluation and found that: i) such content-based features have higher predictive power than code complexity metrics and ii) the use of feature selection, reduction, and combination further improves the prediction performance.
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- 2024
9. Tracking Software Security Topics
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Vu, Phong Minh and Nguyen, Tung Thanh
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Computer Science - Software Engineering ,Computer Science - Artificial Intelligence ,Computer Science - Cryptography and Security ,Computer Science - Information Retrieval - Abstract
Software security incidents occur everyday and thousands of software security reports are announced each month. Thus, it is difficult for software security researchers, engineers, and other stakeholders to follow software security topics of their interests in real-time. In this paper, we propose, SOSK, a novel tool for this problem. SOSK allows a user to import a collection of software security reports. It pre-processes and extracts the most important keywords from the textual description of the reports. Based on the similarity of embedding vectors of keywords, SOSK can expand and/or refine a keyword set from a much smaller set of user-provided keywords. Thus, SOSK allows users to define any topic of their interests and retrieve security reports relevant to that topic effectively. Our preliminary evaluation shows that SOSK can expand keywords and retrieve reports relevant to user requests.
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- 2024
10. Subdivisions and near-linear stable sets
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Nguyen, Tung, Scott, Alex, and Seymour, Paul
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Mathematics - Combinatorics - Abstract
We prove that for every complete graph $K_t$, all graphs $G$ with no induced subgraph isomorphic to a subdivision of $K_t$ have a stable subset of size at least $|G|/{\rm polylog}|G|$. This is close to best possible, because for $t\ge 6$, not all such graphs $G$ have a stable set of linear size, even if $G$ is triangle-free.
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- 2024
11. Trees and near-linear stable sets
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Nguyen, Tung, Scott, Alex, and Seymour, Paul
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Mathematics - Combinatorics - Abstract
When $H$ is a forest, the Gy\'arf\'as-Sumner conjecture implies that every graph $G$ with no induced subgraph isomorphic to $H$ and with bounded clique number has a stable set of linear size. We cannot prove that, but we prove that every such graph $G$ has a stable set of size $|G|^{1-o(1)}$. If $H$ is not a forest, there need not be such a stable set. Second, we prove that when $H$ is a ``multibroom'', there {\em is} a stable set of linear size. As a consequence, we deduce that all multibrooms satisfy a ``fractional colouring'' version of the Gy\'arf\'as-Sumner conjecture. Finally, we discuss extensions of our results to the multicolour setting.
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- 2024
12. Distant digraph domination
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Nguyen, Tung, Scott, Alex, and Seymour, Paul
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Mathematics - Combinatorics - Abstract
A {\em $k$-kernel} in a digraph $G$ is a stable set $X$ of vertices such that every vertex of $G$ can be joined from $X$ by a directed path of length at most $k$. We prove three results about $k$-kernels. First, it was conjectured by Erd\H{o}s and Sz\'ekely in 1976 that every digraph $G$ with no source has a 2-kernel $|K|$ with $|K|\le |G|/2$. We prove this conjecture when $G$ is a ``split digraph'' (that is, its vertex set can be partitioned into a tournament and a stable set), improving a result of Langlois et al., who proved that every split digraph $G$ with no source has a 2-kernel of size at most $2|G|/3$. Second, the Erd\H{o}s-Sz\'ekely conjecture implies that in every digraph $G$ there is a 2-kernel $K$ such that the union of $K$ and its out-neighbours has size at least $|G|/2$. We prove that this is true if $V(G)$ can be partitioned into a tournament and an acyclic set. Third, in a recent paper, Spiro asked whether, for all $k\ge 3$, every strongly-connected digraph $G$ has a $k$-kernel of size at most about $|G|/(k+1)$. This remains open, but we prove that there is one of size at most about $|G|/(k-1)$.
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- 2024
13. On the gcd graphs over polynomial rings and related topics
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Mináč, Ján, Nguyen, Tung T., and Tân, Nguyen Duy
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Mathematics - Number Theory ,Mathematics - Commutative Algebra ,Mathematics - Combinatorics - Abstract
Gcd-graphs over the ring of integers modulo $n$ are a natural generalization of unitary Cayley graphs. The study of these graphs has foundations in various mathematical fields, including number theory, ring theory, and representation theory. Using the theory of Ramanujan sums, it is known that these gcd-graphs have integral spectra; i.e., all their eigenvalues are integers. In this work, inspired by the analogy between number fields and function fields, we define and study gcd-graphs over polynomial rings with coefficients in finite fields. We establish some fundamental properties of these graphs, emphasizing their analogy to their counterparts over $\mathbb{Z}.$, Comment: Comments are welcome!
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- 2024
14. A complete classification of perfect unitary Cayley graphs
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Mináč, Ján, Nguyen, Tung T., and Tân, Nguyen Duy
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Mathematics - Combinatorics ,Mathematics - Rings and Algebras - Abstract
Due to their elegant and simple nature, unitary Cayley graphs have been an active research topic in the literature. These graphs are naturally connected to several branches of mathematics, including number theory, finite algebra, representation theory, and graph theory. In this article, we study the perfectness property of these graphs. More precisely, we provide a complete classification of perfect unitary Cayley graphs associated with finite rings., Comment: Comments are welcome!
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- 2024
15. ClimDetect: A Benchmark Dataset for Climate Change Detection and Attribution
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Yu, Sungduk, White, Brian L., Bhiwandiwalla, Anahita, Hinck, Musashi, Olson, Matthew Lyle, Nguyen, Tung, and Lal, Vasudev
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Computer Science - Computer Vision and Pattern Recognition ,Computer Science - Machine Learning ,Physics - Atmospheric and Oceanic Physics - Abstract
Detecting and attributing temperature increases due to climate change is crucial for understanding global warming and guiding adaptation strategies. The complexity of distinguishing human-induced climate signals from natural variability has challenged traditional detection and attribution (D&A) approaches, which seek to identify specific "fingerprints" in climate response variables. Deep learning offers potential for discerning these complex patterns in expansive spatial datasets. However, lack of standard protocols has hindered consistent comparisons across studies. We introduce ClimDetect, a standardized dataset of over 816k daily climate snapshots, designed to enhance model accuracy in identifying climate change signals. ClimDetect integrates various input and target variables used in past research, ensuring comparability and consistency. We also explore the application of vision transformers (ViT) to climate data, a novel and modernizing approach in this context. Our open-access data and code serve as a benchmark for advancing climate science through improved model evaluations. ClimDetect is publicly accessible via Huggingface dataet respository at: https://huggingface.co/datasets/ClimDetect/ClimDetect.
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- 2024
16. Enhancing Changepoint Detection: Penalty Learning through Deep Learning Techniques
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Nguyen, Tung L and Hocking, Toby Dylan
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Statistics - Machine Learning ,Computer Science - Machine Learning - Abstract
Changepoint detection, a technique for identifying significant shifts within data sequences, is crucial in various fields such as finance, genomics, medicine, etc. Dynamic programming changepoint detection algorithms are employed to identify the locations of changepoints within a sequence, which rely on a penalty parameter to regulate the number of changepoints. To estimate this penalty parameter, previous work uses simple models such as linear or tree-based models. This study introduces a novel deep learning method for predicting penalty parameters, leading to demonstrably improved changepoint detection accuracy on large benchmark supervised labeled datasets compared to previous methods., Comment: 17 pages, 7 figures
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- 2024
17. One Health Surveillance Highlights Circulation of Viruses with Zoonotic Potential in Bats, Pigs, and Humans in Viet Nam
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Alice Latinne, Nguyen Thi Thanh Nga, Nguyen Van Long, Pham Thi Bich Ngoc, Hoang Bich Thuy, PREDICT Consortium, Pham Thanh Long, Nguyen Thanh Phuong, Le Tin Vinh Quang, Nguyen Tung, Vu Sinh Nam, Vu Trong Duoc, Nguyen Duc Thinh, Randal Schoepp, Keersten Ricks, Ken Inui, Pawin Padungtod, Christine K. Johnson, Jonna A. K. Mazet, Chris Walzer, Sarah H. Olson, and Amanda E. Fine
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One Health ,bats ,pigs ,zoonoses ,livestock ,coronavirus ,Microbiology ,QR1-502 - Abstract
A One Health cross-sectoral surveillance approach was implemented to screen biological samples from bats, pigs, and humans at high-risk interfaces for zoonotic viral spillover for five viral families with zoonotic potential in Viet Nam. Over 1600 animal and human samples from bat guano harvesting sites, natural bat roosts, and pig farming operations were tested for coronaviruses (CoVs), paramyxoviruses, influenza viruses, filoviruses and flaviviruses using consensus PCR assays. Human samples were also tested using immunoassays to detect antibodies against eight virus groups. Significant viral diversity, including CoVs closely related to ancestors of pig pathogens, was detected in bats roosting at the human–animal interfaces, illustrating the high risk for CoV spillover from bats to pigs in Viet Nam, where pig density is very high. Season and reproductive period were significantly associated with the detection of bat CoVs, with site-specific effects. Phylogeographic analysis indicated localized viral transmission among pig farms. Our limited human sampling did not detect any known zoonotic bat viruses in human communities living close to the bat cave and harvesting bat guano, but our serological assays showed possible previous exposure to Marburg virus-like (Filoviridae), Crimean–Congo hemorrhagic fever virus-like (Bunyaviridae) viruses and flaviviruses. Targeted and coordinated One Health surveillance helped uncover this viral pathogen emergence hotspot.
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- 2023
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18. Federated PCA on Grassmann Manifold for IoT Anomaly Detection
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Nguyen, Tung-Anh, Le, Long Tan, Nguyen, Tuan Dung, Bao, Wei, Seneviratne, Suranga, Hong, Choong Seon, and Tran, Nguyen H.
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Computer Science - Machine Learning ,Computer Science - Artificial Intelligence ,Computer Science - Cryptography and Security ,Computer Science - Distributed, Parallel, and Cluster Computing - Abstract
With the proliferation of the Internet of Things (IoT) and the rising interconnectedness of devices, network security faces significant challenges, especially from anomalous activities. While traditional machine learning-based intrusion detection systems (ML-IDS) effectively employ supervised learning methods, they possess limitations such as the requirement for labeled data and challenges with high dimensionality. Recent unsupervised ML-IDS approaches such as AutoEncoders and Generative Adversarial Networks (GAN) offer alternative solutions but pose challenges in deployment onto resource-constrained IoT devices and in interpretability. To address these concerns, this paper proposes a novel federated unsupervised anomaly detection framework, FedPCA, that leverages Principal Component Analysis (PCA) and the Alternating Directions Method Multipliers (ADMM) to learn common representations of distributed non-i.i.d. datasets. Building on the FedPCA framework, we propose two algorithms, FEDPE in Euclidean space and FEDPG on Grassmann manifolds. Our approach enables real-time threat detection and mitigation at the device level, enhancing network resilience while ensuring privacy. Moreover, the proposed algorithms are accompanied by theoretical convergence rates even under a subsampling scheme, a novel result. Experimental results on the UNSW-NB15 and TON-IoT datasets show that our proposed methods offer performance in anomaly detection comparable to nonlinear baselines, while providing significant improvements in communication and memory efficiency, underscoring their potential for securing IoT networks., Comment: Accepted for publication at IEEE/ACM Transactions on Networking
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- 2024
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19. LICO: Large Language Models for In-Context Molecular Optimization
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Nguyen, Tung and Grover, Aditya
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Computer Science - Machine Learning ,Computer Science - Artificial Intelligence ,Physics - Chemical Physics ,Quantitative Biology - Biomolecules ,Quantitative Biology - Quantitative Methods - Abstract
Optimizing black-box functions is a fundamental problem in science and engineering. To solve this problem, many approaches learn a surrogate function that estimates the underlying objective from limited historical evaluations. Large Language Models (LLMs), with their strong pattern-matching capabilities via pretraining on vast amounts of data, stand out as a potential candidate for surrogate modeling. However, directly prompting a pretrained language model to produce predictions is not feasible in many scientific domains due to the scarcity of domain-specific data in the pretraining corpora and the challenges of articulating complex problems in natural language. In this work, we introduce LICO, a general-purpose model that extends arbitrary base LLMs for black-box optimization, with a particular application to the molecular domain. To achieve this, we equip the language model with a separate embedding layer and prediction layer, and train the model to perform in-context predictions on a diverse set of functions defined over the domain. Once trained, LICO can generalize to unseen molecule properties simply via in-context prompting. LICO achieves state-of-the-art performance on PMO, a challenging molecular optimization benchmark comprising over 20 objective functions.
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- 2024
20. Probing the Decision Boundaries of In-context Learning in Large Language Models
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Zhao, Siyan, Nguyen, Tung, and Grover, Aditya
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Computer Science - Machine Learning ,Computer Science - Artificial Intelligence ,Computer Science - Computation and Language - Abstract
In-context learning is a key paradigm in large language models (LLMs) that enables them to generalize to new tasks and domains by simply prompting these models with a few exemplars without explicit parameter updates. Many attempts have been made to understand in-context learning in LLMs as a function of model scale, pretraining data, and other factors. In this work, we propose a new mechanism to probe and understand in-context learning from the lens of decision boundaries for in-context binary classification. Decision boundaries are straightforward to visualize and provide important information about the qualitative behavior of the inductive biases of standard classifiers. To our surprise, we find that the decision boundaries learned by current LLMs in simple binary classification tasks are often irregular and non-smooth, regardless of linear separability in the underlying task. This paper investigates the factors influencing these decision boundaries and explores methods to enhance their generalizability. We assess various approaches, including training-free and fine-tuning methods for LLMs, the impact of model architecture, and the effectiveness of active prompting techniques for smoothing decision boundaries in a data-efficient manner. Our findings provide a deeper understanding of in-context learning dynamics and offer practical improvements for enhancing robustness and generalizability of in-context learning., Comment: 18 pages, code at https://github.com/siyan-zhao/ICL_decision_boundary
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- 2024
21. $i$REPO: $i$mplicit Reward Pairwise Difference based Empirical Preference Optimization
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Le, Long Tan, Shu, Han, Nguyen, Tung-Anh, Hong, Choong Seon, and Tran, Nguyen H.
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Computer Science - Artificial Intelligence ,Computer Science - Machine Learning - Abstract
While astonishingly capable, large Language Models (LLM) can sometimes produce outputs that deviate from human expectations. Such deviations necessitate an alignment phase to prevent disseminating untruthful, toxic, or biased information. Traditional alignment methods based on reinforcement learning often struggle with the identified instability, whereas preference optimization methods are limited by their overfitting to pre-collected hard-label datasets. In this paper, we propose a novel LLM alignment framework named $i$REPO, which utilizes implicit Reward pairwise difference regression for Empirical Preference Optimization. Particularly, $i$REPO employs self-generated datasets labelled by empirical human (or AI annotator) preference to iteratively refine the aligned policy through a novel regression-based loss function. Furthermore, we introduce an innovative algorithm backed by theoretical guarantees for achieving optimal results under ideal assumptions and providing a practical performance-gap result without such assumptions. Experimental results with Phi-2 and Mistral-7B demonstrate that $i$REPO effectively achieves self-alignment using soft-label, self-generated responses and the logit of empirical AI annotators. Furthermore, our approach surpasses preference optimization baselines in evaluations using the Language Model Evaluation Harness and Multi-turn benchmarks., Comment: Under Review
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- 2024
22. Maxillary distraction osteogenesis and a Le Fort I osteotomy for severe maxillary retrognathia in cleft lip and palate: a case report
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Fowler Peter V., Steenberg Leon, and Nguyen Tung
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Dentistry ,RK1-715 - Abstract
The correction of severe maxillary retrognathia in patients presenting with a cleft palate is challenging due to the complexity of the orthodontic preparation and the magnitude of the surgical movements required, along with the relatively high risk of relapse.
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- 2020
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23. Pain management inequities by demographic and geriatric‐related variables in older adult inpatients
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Rambachan, Aksharananda, Neilands, Torsten B, Karliner, Leah, Covinsky, Kenneth, Fang, Margaret, and Nguyen, Tung
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Biomedical and Clinical Sciences ,Clinical Sciences ,Health Sciences ,Dementia ,Alzheimer's Disease including Alzheimer's Disease Related Dementias (AD/ADRD) ,Alzheimer's Disease ,Neurosciences ,Neurodegenerative ,Aging ,Clinical Research ,Chronic Pain ,Pain Research ,Acquired Cognitive Impairment ,Brain Disorders ,Neurological ,equity ,geriatrics ,hospital medicine ,pain management ,Medical and Health Sciences ,Geriatrics ,Biomedical and clinical sciences ,Health sciences ,Psychology - Abstract
BackgroundPain is ubiquitous, yet understudied. The objective of this study was to analyze inequities in pain assessment and management for hospitalized older adults focusing on demographic and geriatric-related variables.MethodsThis was a retrospective cohort study from January 2013 through September 2021 of all adults 65 years or older on the general medicine service at UCSF Medical Center. Primary exposures included (1) demographic variables including race/ethnicity and limited English proficiency (LEP) status and (2) geriatric-related variables including age, dementia or mild cognitive impairment diagnosis, hearing or visual impairment, end-of-life care, and geriatrics consult involvement. Primary outcomes included (1) adjusted odds of numeric pain assessment versus other assessments and (2) adjusted opioids administered, measured by morphine milligram equivalents (MME).ResultsA total of 15,809 patients were included across 27,857 hospitalizations with 1,378,215 pain assessments, with a mean age of 77.8 years old. Patients were 47.4% White, 26.3% with LEP, 49.6% male, and 50.4% female. Asian (OR 0.75, 95% CI 0.70-0.80), Latinx (OR 0.90, 95% CI 0.83-0.99), and Native Hawaiian or Pacific Islander (OR 0.77, 95% CI 0.64-0.93) patients had lower odds of a numeric assessment, compared with White patients. Patients with LEP (OR 0.70, 95% CI 0.66-0.74) had lower odds of a numeric assessment, compared with English-speaking patients. Patients with dementia, hearing impairment, patients 75+, and at end-of-life were all less likely to receive a numeric assessment. Compared with White patients (86 MME, 95% CI 77-96), Asian patients (55 MME, 95% CI 46-65) received fewer opioids. Patients with LEP, dementia, hearing impairment and those 75+ years old also received significantly fewer opioids.ConclusionOlder, hospitalized, general medicine patients from minoritized groups and with geriatric-related conditions are uniquely vulnerable to inequitable pain assessment and management. These findings raise concerns for pain underassessment and undertreatment.
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- 2024
24. An App-Based Physical Activity Intervention in Community-Dwelling Chinese-, Tagalog-, and Vietnamese-Speaking Americans: Single-Arm Intervention Study.
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Nguyen, Antony, Yu, Filmer, Park, Linda, Fukuoka, Yoshimi, Wong, Ching, Gildengorin, Ginny, Nguyen, Tung, Tsoh, Janice, and Jih, Jane
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Asian Americans ,Chinese ,Filipino ,Vietnamese ,acceptability ,adult ,adults ,app ,app-based ,application ,applications ,apps ,community-based ,community-dwelling ,cultural ,culturally ,evidence-based ,feasibility ,intervention ,interventions ,lifestyle ,linguistic ,linguistically ,mHealth ,mobile app ,mobile health ,mobile phone ,multicomponent ,multilingual ,physical activity ,physical activity tracker ,pilot study ,sociodemographic ,tracker ,trackers - Abstract
BACKGROUND: Physical inactivity is associated with adverse health outcomes among Asian Americans, who exhibit the least adherence to physical activity guidelines compared with other racial and ethnic groups. Mobile app-based interventions are a promising approach to promote healthy behaviors. However, there is a lack of app-based interventions focused on improving physical activity among Asian Americans whose primary language is not English. OBJECTIVE: This pilot study aimed to assess the feasibility and acceptability of a 5-week intervention using a culturally and linguistically adapted, evidence-based mobile phone app with an accelerometer program, to promote physical activity among Chinese-, Tagalog-, or Vietnamese-speaking Americans. METHODS: Participants were recruited through collaborations with community-based organizations. The intervention was adapted from a 12-month physical activity randomized controlled trial involving the app and accelerometer for English-speaking adults. Sociodemographic characteristics, lifestyle factors, and physical measurements were collected at the baseline visit. A 7-day run-in period was conducted to screen for the participants who could wear a Fitbit One (Fitbit LLC) accelerometer and complete the apps daily step diary. During the 4-week intervention period, participants wore the accelerometer and reported their daily steps in the app. Participants also received daily messages to reinforce key contents taught during an in-person educational session, remind them to input steps, and provide tailored feedback. Feasibility measures were the percentage of eligible participants completing the run-in period and the percentage of participants who used the app diary for at least 5 out of 7 days during the intervention period. We conducted poststudy participant interviews to explore overall intervention acceptability. RESULTS: A total of 19 participants were enrolled at the beginning of the study with a mean age of 47 (SD 13.3; range 29-70) years, and 58% (n=11) of them were female. Of the participants, 26% (n=5) were Chinese, 32% (n=6) were Vietnamese, and 42% (n=8) were Filipino. All participants met the run-in criteria to proceed with the intervention. Adherence to the app diary ranged from 74% (n=14) in week 2 to 95% (n=18) in week 4. The daily average steps per week from accelerometers increased each week from 8451 (SD 3378) steps during the run-in period to 10,930 (SD 4213) steps in week 4. Participants reported positive experiences including an increased motivation to walk and the enjoyment of being able to monitor their physical activity. CONCLUSIONS: This is the first pilot study of a multicomponent intervention and evidence-based mobile phone app to promote physical activity among Asian Americans who use apps in traditional Chinese, Tagalog, or Vietnamese, which demonstrated high feasibility and acceptability. Future work focused on multilingual mobile apps to address disparities in physical inactivity among Asian Americans should be considered.
- Published
- 2024
25. Rank-Preference Consistency as the Appropriate Metric for Recommender Systems
- Author
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Nguyen, Tung and Uhlmann, Jeffrey
- Subjects
Computer Science - Information Retrieval - Abstract
In this paper we argue that conventional unitary-invariant measures of recommender system (RS) performance based on measuring differences between predicted ratings and actual user ratings fail to assess fundamental RS properties. More specifically, posing the optimization problem as one of predicting exact user ratings provides only an indirect suboptimal approximation for what RS applications typically need, which is an ability to accurately predict user preferences. We argue that scalar measures such as RMSE and MAE with respect to differences between actual and predicted ratings are only proxies for measuring RS ability to accurately estimate user preferences. We propose what we consider to be a measure that is more fundamentally appropriate for assessing RS performance, rank-preference consistency, which simply counts the number of prediction pairs that are inconsistent with the user's expressed product preferences. For example, if an RS predicts the user will prefer product A over product B, but the user's withheld ratings indicate s/he prefers product B over A, then rank-preference consistency has been violated. Our test results conclusively demonstrate that methods tailored to optimize arbitrary measures such as RMSE are not generally effective at accurately predicting user preferences. Thus, we conclude that conventional methods used for assessing RS performance are arbitrary and misleading.
- Published
- 2024
26. On certain properties of the $p$-unitary Cayley graph over a finite ring
- Author
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Nguyen, Tung T. and Tân, Nguyen Duy
- Subjects
Mathematics - Combinatorics ,05C25, 05C50, 05C51 - Abstract
In recent work, we study certain Cayley graphs associated with a finite commutative ring and their multiplicative subgroups. Among various results that we prove, we provide the necessary and sufficient conditions for such a Cayley graph to be prime. In this paper, we continue this line of research. Specifically, we investigate some basic properties of certain $p$-unitary Cayeley graphs associated with a finite commutative ring. In particular, under some mild conditions, we provide the necessary and sufficient conditions for this graph to be prime., Comment: Comments are welcome!
- Published
- 2024
27. Graphs without a 3-connected subgraph are 4-colorable
- Author
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Bonnet, Édouard, Feghali, Carl, Nguyen, Tung, Scott, Alex, Seymour, Paul, Thomassé, Stéphan, and Trotignon, Nicolas
- Subjects
Mathematics - Combinatorics ,Computer Science - Discrete Mathematics ,05C15, 05C40 ,G.2.2 - Abstract
In 1972, Mader showed that every graph without a 3-connected subgraph is 4-degenerate and thus 5-colorable}. We show that the number 5 of colors can be replaced by 4, which is best possible., Comment: 13 pages
- Published
- 2024
28. ChaosBench: A Multi-Channel, Physics-Based Benchmark for Subseasonal-to-Seasonal Climate Prediction
- Author
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Nathaniel, Juan, Qu, Yongquan, Nguyen, Tung, Yu, Sungduk, Busecke, Julius, Grover, Aditya, and Gentine, Pierre
- Subjects
Computer Science - Computer Vision and Pattern Recognition ,Computer Science - Computers and Society - Abstract
Accurate prediction of climate in the subseasonal-to-seasonal scale is crucial for disaster preparedness and robust decision making amidst climate change. Yet, forecasting beyond the weather timescale is challenging because it deals with problems other than initial condition, including boundary interaction, butterfly effect, and our inherent lack of physical understanding. At present, existing benchmarks tend to have shorter forecasting range of up-to 15 days, do not include a wide range of operational baselines, and lack physics-based constraints for explainability. Thus, we propose ChaosBench, a challenging benchmark to extend the predictability range of data-driven weather emulators to S2S timescale. First, ChaosBench is comprised of variables beyond the typical surface-atmospheric ERA5 to also include ocean, ice, and land reanalysis products that span over 45 years to allow for full Earth system emulation that respects boundary conditions. We also propose physics-based, in addition to deterministic and probabilistic metrics, to ensure a physically-consistent ensemble that accounts for butterfly effect. Furthermore, we evaluate on a diverse set of physics-based forecasts from four national weather agencies as baselines to our data-driven counterpart such as ViT/ClimaX, PanguWeather, GraphCast, and FourCastNetV2. Overall, we find methods originally developed for weather-scale applications fail on S2S task: their performance simply collapse to an unskilled climatology. Nonetheless, we outline and demonstrate several strategies that can extend the predictability range of existing weather emulators, including the use of ensembles, robust control of error propagation, and the use of physics-informed models. Our benchmark, datasets, and instructions are available at https://leap-stc.github.io/ChaosBench., Comment: Accepted as Oral in NeurIPS'24 D&B Track
- Published
- 2024
29. Numerical Investigation of Load Transfer in Geosynthetic-Reinforced Embankments Over Cavities: Effects of Opening Process and Cyclic Loading
- Author
-
Pham, Minh-Tuan, Nguyen, Duc-Duy, Nguyen, Tung-Duong, and Pham, Van-Hung
- Published
- 2024
- Full Text
- View/download PDF
30. Coronavirus testing indicates transmission risk increases along wildlife supply chains for human consumption in Viet Nam, 2013-2014.
- Author
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Nguyen Quynh Huong, Nguyen Thi Thanh Nga, Nguyen Van Long, Bach Duc Luu, Alice Latinne, Mathieu Pruvot, Nguyen Thanh Phuong, Le Tin Vinh Quang, Vo Van Hung, Nguyen Thi Lan, Nguyen Thi Hoa, Phan Quang Minh, Nguyen Thi Diep, Nguyen Tung, Van Dang Ky, Scott I Roberton, Hoang Bich Thuy, Martin Gilbert, Leanne Wicker, Jonna A K Mazet, Christine Kreuder Johnson, Tracey Goldstein, Alex Tremeau-Bravard, Victoria Ontiveros, Damien O Joly, Chris Walzer, Amanda E Fine, and Sarah H Olson
- Subjects
Medicine ,Science - Abstract
Outbreaks of emerging coronaviruses in the past two decades and the current pandemic of a novel coronavirus (SARS-CoV-2) that emerged in China highlight the importance of this viral family as a zoonotic public health threat. To gain a better understanding of coronavirus presence and diversity in wildlife at wildlife-human interfaces in three southern provinces in Viet Nam 2013-2014, we used consensus Polymerase Chain Reactions to detect coronavirus sequences. In comparison to previous studies, we observed high proportions of positive samples among field rats (34.0%, 239/702) destined for human consumption and insectivorous bats in guano farms (74.8%, 234/313) adjacent to human dwellings. Most notably among field rats, the odds of coronavirus RNA detection significantly increased along the supply chain from field rats sold by traders (reference group; 20.7% positivity, 39/188) by a factor of 2.2 for field rats sold in large markets (32.0%, 116/363) and 10.0 for field rats sold and served in restaurants (55.6%, 84/151). Coronaviruses were also detected in rodents on the majority of wildlife farms sampled (60.7%, 17/28). These coronaviruses were found in the Malayan porcupines (6.0%, 20/331) and bamboo rats (6.3%, 6/96) that are raised on wildlife farms for human consumption as food. We identified six known coronaviruses in bats and rodents, clustered in three Coronaviridae genera, including the Alpha-, Beta-, and Gammacoronaviruses. Our analysis also suggested either mixing of animal excreta in the environment or interspecies transmission of coronaviruses, as both bat and avian coronaviruses were detected in rodent feces on wildlife farms. The mixing of multiple coronaviruses, and their apparent amplification along the wildlife supply chain into restaurants, suggests maximal risk for end consumers and likely underpins the mechanisms of zoonotic spillover to people.
- Published
- 2020
- Full Text
- View/download PDF
31. A counterexample to the coarse Menger conjecture
- Author
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Nguyen, Tung, Scott, Alex, and Seymour, Paul
- Subjects
Mathematics - Combinatorics ,05C12, 05C38 - Abstract
It was conjectured, independently by two sets of authors, that for all integers $k,d\ge 1$ there exists $\ell>0$, such that if $S,T$ are subsets of vertices of a graph $G$, then either there are $k$ paths between $S,T$, pairwise at distance at least $d$, or there is a set $X\subseteq V(G)$ with $|X|\le k-1$ such that every path between $S,T$ contains a vertex with distance at most $\ell$ from some member of $X$. The result is known for $k\le 2$, but we will show that it is false for all $k\ge 3$, even if $G$ is constrained to have maximum degree at most three. We also give a proof of the result when $k=2$ that is simpler than the previous proofs.
- Published
- 2024
32. On prime Cayley graphs
- Author
-
Chudnovsky, Maria, Cizek, Michal, Crew, Logan, Mináč, Ján, Nguyen, Tung T., Spirkl, Sophie, and Tân, Nguyên Duy
- Subjects
Mathematics - Combinatorics ,Mathematics - Group Theory - Abstract
The decomposition of complex networks into smaller, interconnected components is a central challenge in network theory with a wide range of potential applications. In this paper, we utilize tools from group theory and ring theory to study this problem when the network is a Cayley graph. In particular, we answer the following question: Which Cayley graphs are prime?
- Published
- 2024
33. Correlates of supportive care needs among Asian Americans with colorectal, liver, or lung cancer from a web‐based patient navigation portal intervention: The Patient COUNTS study
- Author
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Wang, Katarina, Chu, Janet N, Oh, Debora L, Shariff‐Marco, Salma, Allen, Laura, Kuo, Mei‐Chin, Wong, Ching, Bui, Hoan, Chen, Junlin, Li, Feng Ming, Ma, Carmen, Truong, Angeline, Gomez, Scarlett L, Nguyen, Tung T, and Tsoh, Janice Y
- Subjects
Biomedical and Clinical Sciences ,Oncology and Carcinogenesis ,Clinical Research ,Rehabilitation ,Aging ,Digestive Diseases ,Behavioral and Social Science ,Colo-Rectal Cancer ,Cancer ,Management of diseases and conditions ,7.1 Individual care needs ,Good Health and Well Being ,Adult ,Female ,Humans ,Male ,Middle Aged ,Asian ,Colorectal Neoplasms ,Internet ,Lung Neoplasms ,Patient Navigation ,Quality of Life ,Liver Neoplasms ,Patient Portals ,Asian American ,cancer ,cultural competence ,cultural humility ,multilingual ,patient navigation ,supportive care needs ,Oncology and carcinogenesis - Abstract
BackgroundCancer is the leading cause of death among Asian Americans, who often face barriers to cancer care. Cancer supportive care needs among Asian Americans remain understudied.AimsWe examined cancer supportive care needs and participant factors correlated with these needs, identified profiles of supportive care needs, and examined whether needs profiles are associated with quality of life among Asian American adults.Methods and resultsWe recruited 47 Asian American adults with colorectal, liver, or lung cancer who spoke Chinese, English, or Vietnamese, and were starting or undergoing cancer treatment. We assessed cancer supportive care needs in four domains: cancer information, daily living, behavioral health, and language assistance. Hierarchical cluster analysis was used to identify clusters of participants based on their supportive need profiles to further examine the association between need profiles and quality of life (QoL) assessed by the Functional Assessment of Cancer Therapy. Participants (mean age = 57.6) included 72% males and 62% spoke English less than very well. Older participants (age ≥ 65) and those with annual income
- Published
- 2024
34. Induced subgraph density. VI. Bounded VC-dimension
- Author
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Nguyen, Tung, Scott, Alex, and Seymour, Paul
- Subjects
Mathematics - Combinatorics - Abstract
We confirm a conjecture of Fox, Pach, and Suk, that for every $d>0$, there exists $c>0$ such that every $n$-vertex graph of VC-dimension at most $d$ has a clique or stable set of size at least $n^c$. This implies that, in the language of model theory, every graph definable in NIP structures has a clique or anti-clique of polynomial size, settling a conjecture of Chernikov, Starchenko, and Thomas. Our result also implies that every two-colourable tournament satisfies the tournament version of the Erd\H{o}s-Hajnal conjecture, which completes the verification of the conjecture for six-vertex tournaments. The result extends to uniform hypergraphs of bounded VC-dimension as well. The proof method uses the ultra-strong regularity lemma for graphs of bounded VC-dimension proved by Lov\'asz and Szegedy and the method of iterative sparsification introduced by the authors in an earlier paper., Comment: 11 pages, minor revisions
- Published
- 2023
35. Induced subgraph density. VII. The five-vertex path
- Author
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Nguyen, Tung, Scott, Alex, and Seymour, Paul
- Subjects
Mathematics - Combinatorics - Abstract
We prove the Erd\H{o}s-Hajnal conjecture for the five-vertex path $P_5$; that is, there exists $c>0$ such that every $n$-vertex graph with no induced $P_5$ has a clique or stable set of size at least $n^c$. This completes the verification of the Erd\H{o}s-Hajnal property of all five-vertex graphs. Indeed, we show a stronger statement, that $P_5$ satisfies the polynomial version of a theorem of R\"odl. To achieve this, we combine simple probabilistic and structural ideas with the iterative sparsification framework introduced in the series., Comment: 15 pages
- Published
- 2023
36. A Study on Social Robot Behavior in Group Conversation
- Author
-
Nguyen, Tung, Nichols, Eric, and Gomez, Randy
- Subjects
Computer Science - Human-Computer Interaction ,Computer Science - Artificial Intelligence - Abstract
Recently, research in human-robot interaction began to consider a robot's influence at the group level. Despite the recent growth in research investigating the effects of robots within groups of people, our overall understanding of what happens when robots are placed within groups or teams of people is still limited. This paper investigates several key problems for social robots that manage conversations in a group setting, where the number of participants is more than two. In a group setting, the conversation dynamics are a lot more complicated than the conventional one-to-one conversation, thus, there are more challenges need to be solved., Comment: 5 pages
- Published
- 2023
37. Scaling transformer neural networks for skillful and reliable medium-range weather forecasting
- Author
-
Nguyen, Tung, Shah, Rohan, Bansal, Hritik, Arcomano, Troy, Madireddy, Sandeep, Maulik, Romit, Kotamarthi, Veerabhadra, Foster, Ian, and Grover, Aditya
- Subjects
Physics - Atmospheric and Oceanic Physics ,Computer Science - Artificial Intelligence ,Computer Science - Machine Learning - Abstract
Weather forecasting is a fundamental problem for anticipating and mitigating the impacts of climate change. Recently, data-driven approaches for weather forecasting based on deep learning have shown great promise, achieving accuracies that are competitive with operational systems. However, those methods often employ complex, customized architectures without sufficient ablation analysis, making it difficult to understand what truly contributes to their success. Here we introduce Stormer, a simple transformer model that achieves state-of-the-art performance on weather forecasting with minimal changes to the standard transformer backbone. We identify the key components of Stormer through careful empirical analyses, including weather-specific embedding, randomized dynamics forecast, and pressure-weighted loss. At the core of Stormer is a randomized forecasting objective that trains the model to forecast the weather dynamics over varying time intervals. During inference, this allows us to produce multiple forecasts for a target lead time and combine them to obtain better forecast accuracy. On WeatherBench 2, Stormer performs competitively at short to medium-range forecasts and outperforms current methods beyond 7 days, while requiring orders-of-magnitude less training data and compute. Additionally, we demonstrate Stormer's favorable scaling properties, showing consistent improvements in forecast accuracy with increases in model size and training tokens. Code and checkpoints will be made publicly available.
- Published
- 2023
38. A Note on Finite Number Rings
- Author
-
Hwang, Suk-Geun, Jeon, Woo, Nam, Ki-Bong, and Nguyen, Tung T.
- Subjects
Mathematics - Rings and Algebras ,11T06, 11T30, 11Z05, 97H40 - Abstract
We define the finite number ring ${\Bbb Z}_n [\sqrt [m] r]$ where $m,n$ are positive integers and $r$ in an integer akin to the definition of the Gaussian integer ${\Bbb Z}[i]$. This idea is also introduced briefly in [7]. By definition, this finite number ring ${\Bbb Z}_n [\sqrt [m] r]$ is naturally isomorphic to the ring ${\Bbb Z}_n[x]/{\langle x^m-r \rangle}$. From an educational standpoint, this description offers a straightforward and elementary presentation of this finite ring, making it suitable for readers who do not have extensive exposure to abstract algebra. We discuss various arithmetical properties of this ring. In particular, when $n=p$ is a prime number and $\mathbb{Z}_p$ contains a primitive $m$-root of unity, we describe the structure of $\mathbb{Z}_n[\sqrt[m]{r}]$ explicitly., Comment: Expository paper. Comments are welcome!
- Published
- 2023
39. HOSSemEval-EB23: a robust dataset for aspect-based sentiment analysis of hospitality reviews
- Author
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Doan, Tram T., Tran, Thuan Q., Le, Dat T., Tran, Anh H., Nguyen, An T., Le, Tran Hoai An, Doan, Tran Nguyen Tung, Huynh, Son T., and Nguyen, Binh T.
- Published
- 2024
- Full Text
- View/download PDF
40. Distributionally Robust Federated Learning for Mobile Edge Networks
- Author
-
Le, Long Tan, Nguyen, Tung-Anh, Nguyen, Tuan-Dung, Tran, Nguyen H., Truong, Nguyen Binh, Vo, Phuong L., Hung, Bui Thanh, and Le, Tuan Anh
- Published
- 2024
- Full Text
- View/download PDF
41. Efficient Methane Dry Reforming Process with Low Nickel Loading for Greenhouse Gas Mitigation
- Author
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Pham, Cham Q., Alsaiari, Mabkhoot, Hieu, Nguyen Huu, Pham, Thuy-Phuong T., Le Phuong, Duy Ha, Rajamohan, Natarajan, Setiabudi, H. D., Vo, Dai-Viet N., Trinh, Thanh H., Pham, Phuong T.H., and Nguyen, Tung M.
- Published
- 2024
- Full Text
- View/download PDF
42. ExPT: Synthetic Pretraining for Few-Shot Experimental Design
- Author
-
Nguyen, Tung, Agrawal, Sudhanshu, and Grover, Aditya
- Subjects
Computer Science - Machine Learning ,Computer Science - Artificial Intelligence - Abstract
Experimental design is a fundamental problem in many science and engineering fields. In this problem, sample efficiency is crucial due to the time, money, and safety costs of real-world design evaluations. Existing approaches either rely on active data collection or access to large, labeled datasets of past experiments, making them impractical in many real-world scenarios. In this work, we address the more challenging yet realistic setting of few-shot experimental design, where only a few labeled data points of input designs and their corresponding values are available. We approach this problem as a conditional generation task, where a model conditions on a few labeled examples and the desired output to generate an optimal input design. To this end, we introduce Experiment Pretrained Transformers (ExPT), a foundation model for few-shot experimental design that employs a novel combination of synthetic pretraining with in-context learning. In ExPT, we only assume knowledge of a finite collection of unlabelled data points from the input domain and pretrain a transformer neural network to optimize diverse synthetic functions defined over this domain. Unsupervised pretraining allows ExPT to adapt to any design task at test time in an in-context fashion by conditioning on a few labeled data points from the target task and generating the candidate optima. We evaluate ExPT on few-shot experimental design in challenging domains and demonstrate its superior generality and performance compared to existing methods. The source code is available at https://github.com/tung-nd/ExPT.git., Comment: 2023 Conference on Neural Information Processing Systems (NeurIPS)
- Published
- 2023
43. Federated Deep Equilibrium Learning: A Compact Shared Representation for Edge Communication Efficiency
- Author
-
Le, Long Tan, Nguyen, Tuan Dung, Nguyen, Tung-Anh, Hong, Choong Seon, and Tran, Nguyen H.
- Subjects
Computer Science - Machine Learning ,Computer Science - Distributed, Parallel, and Cluster Computing - Abstract
Federated Learning (FL) is a prominent distributed learning paradigm facilitating collaboration among nodes within an edge network to co-train a global model without centralizing data. By shifting computation to the network edge, FL offers robust and responsive edge-AI solutions and enhance privacy-preservation. However, deploying deep FL models within edge environments is often hindered by communication bottlenecks, data heterogeneity, and memory limitations. To address these challenges jointly, we introduce FeDEQ, a pioneering FL framework that effectively employs deep equilibrium learning and consensus optimization to exploit a compact shared data representation across edge nodes, allowing the derivation of personalized models specific to each node. We delve into a unique model structure composed of an equilibrium layer followed by traditional neural network layers. Here, the equilibrium layer functions as a global feature representation that edge nodes can adapt to personalize their local layers. Capitalizing on FeDEQ's compactness and representation power, we present a novel distributed algorithm rooted in the alternating direction method of multipliers (ADMM) consensus optimization and theoretically establish its convergence for smooth objectives. Experiments across various benchmarks demonstrate that FeDEQ achieves performance comparable to state-of-the-art personalized methods while employing models of up to 4 times smaller in communication size and 1.5 times lower memory footprint during training.
- Published
- 2023
44. On the arithmetic of the join rings over finite fields
- Author
-
Chebolu, Sunil K., Merzel, Jonathan, Mináč, Ján, Nguyen, Tung T., Pasini, Federico, and Tân, Nguyên Duy
- Subjects
Mathematics - Rings and Algebras ,Mathematics - Number Theory - Abstract
Given a collection $\{ G_i\}_{i=1}^d$ of finite groups and a ring $R$, we have previously introduced and studied certain foundational properties of the join ring $\mathcal{J}_{G_1, G_2, \ldots, G_d}(R)$. This ring bridges two extreme worlds: matrix rings $M_n(R)$ on one end, and group rings $R[G]$ on the other. The construction of this ring was motivated by various problems in graph theory, network theory, nonlinear dynamics, and neuroscience. In this paper, we continue our investigations of this ring, focusing more on its arithmetic properties. We begin by constructing a generalized augmentation map that gives a structural decomposition of this ring. This decomposition allows us to compute the zeta function of the join of group rings. We show that the join of group rings is a natural home for studying the concept of simultaneous primitive roots for a given set of primes. This concept is related to the order of the unit group of the join of group rings. Finally, we characterize the join of group rings over finite fields with the property that the order of every unit divides a fixed number. Remarkably, Mersenne and Fermat primes unexpectedly emerge within the context of this exploration., Comment: 21 pages
- Published
- 2023
45. MACROSCOPIC CROSS SECTIONS GENERATION BY MONTE CARLO CODE MCS FOR FAST REACTOR ANALYSIS
- Author
-
Nguyen Tung Dong Cao, Lee Hyunsuk, Du Xianan, Dos Vutheam, Tran Tuan Quoc, and Lee Deokjung
- Subjects
monte carlo ,multi-group cross section ,fast reactor ,mcs ,nodal diffusion ,Physics ,QC1-999 - Abstract
Recent researches have become more interested in the feasibility of using Monte Carlo (MC) code to generate multi-group (MG) cross sections (XSs) for fast reactor analysis using nodal diffusion codes. The current study, therefore, presents a brief methodology for MG XSs generation by the in-house UNIST MC code MCS, which can be compatibly utilized in nodal diffusion codes, PARCS and RAST-K. The applicability of the methodology is quantified on the sodium fast reactor (SFR) ABR-1000 design with a metallic fuel from the OECD/NEA SRF benchmark. The few-group XSs generated by MCS with a two-dimensional (2D) fuel assembly geometry are well consistent with those of SERPENT 2. Furthermore, the simulation of beginning-of-cycle (BOC) steady-state three-dimensional (3D) whole-core problem with PARCS and RAST-K is conducted using the generated 24-group XSs by MCS. The nodal diffusion solutions, including the core keff, power profiles and various of reactivity parameters, are compared to reference whole-core results obtained by MC code MCS. Overall, the code-to-code comparison indicates a reasonable agreement between deterministic and stochastic codes, with the difference in keff less than 100 pcm and the root-mean-square (RMS) error in assembly power less than 1.15%. Therefore, it is successfully demonstrated that the employment of the MG XSs generation by MCS for nodal diffusion codes is feasible to accurately perform analyses for fast reactors.
- Published
- 2021
- Full Text
- View/download PDF
46. Virtual BUILD Research Collaboratory: A biomedical data science training using innovative pedagogy to address structures of racism and inequitable stress for undergraduates of color.
- Author
-
Ceberio, Niquo, Le, Peter, Bailey, Jasmón, Vernard, Sonthonax, Coleman, Nichole, Carrasco, Yazmin, King, Telisa, Bibbins-Domingo, Kirsten, Nguyen, Tung, Parangan-Smith, Audrey, Uwaezuoke, Kelechi, Rivers, Robert, Watson, Kenjus, Márquez-Magaña, Leticia, and Mehta, Kala
- Subjects
Humans ,Racism ,Data Science ,Workforce ,Biomedical Research ,Students - Abstract
OBJECTIVE: The unprecedented events of 2020 required a pivot in scientific training to better prepare the biomedical research workforce to address global pandemics, structural racism, and social inequities that devastate human health individually and erode it collectively. Furthermore, this pivot had to be accomplished in the virtual environment given the nation-wide lockdown. METHODS: These needs and context led to leveraging of the San Francisco Building Infrastructure Leading to Diversity (SF BUILD) theories of change to innovate a Virtual BUILD Research Collaboratory (VBRC). The purpose of VBRC was to train Black, Indigenous, and people of color (BIPOC) students to apply their unique perspectives to biomedical research. These training activities were evaluated using a pre-post survey design that included both validated and new psychosocial scales. A new scale was piloted to measure culturally relevant pedagogy. RESULTS: VBRC scholars increased science identity on two items: thinking of myself as a scientist (+1point, p = 0.006) and belonging to a community of scientists (+1point, p = 0.069). Overall, scholars perceived stress also decreased over VBRC (-2.35 points, p = 0.02). Post VBRC, scholars had high agency scores (μ = 11.02, Md = 12, range = 6-12, σ = 1.62) and cultural humility scores (μ = 22.11, Md = 23, range = 12-24, σ = 2.71). No notable race/ethnic differences were found in any measures. CONCLUSIONS: Taken together, our innovative approach to data science training for BIPOC in unprecedented times shows promise for better preparing the workforce critically needed to address the fundamental gaps in knowledge at the intersection of public health, structural racism, and biomedical sciences.
- Published
- 2024
47. Assessment of climate change impact on river flow regimes in The Red River Delta, Vietnam – A case study of the Nhue-Day River Basin
- Author
-
Phan Cao Duong, Alexandra Nauditt, Do Hoai Nam, and Nguyen Tung Phong
- Subjects
Modeling ,Flooding ,Drought ,Hydrology ,Trends ,Streamflow ,Geography. Anthropology. Recreation ,Environmental sciences ,GE1-350 - Abstract
Global warming has caused dramatic changes in regional climate variability, particularly regarding fluctuations in temperature and rainfall. Thus, it is predicted that river flow regimes will be altered accordingly. The purpose of this paper is to present the results of modeling such changes by simulating discharge using the HEC-HMS model. The precipitation was projected using super-high resolution multiple climate models (20 km resolution) with newly updated emission scenarios as the input for the HEC-HMS model for flow analysis at the Red River Basin in the northern area of Vietnam. The findings showed that climate change impact on the river flow regimes tend towards a decrease in the dry season and a longer duration of flood flow. A slight runoff reduction is simulated for November while a considerable runoff increase is modeled for July and August amounting to 30% and 25%, respectively. The discharge scenarios serve as a basis for water managers to develop suitable adaptation methods and responses on the river basin scale.
- Published
- 2016
- Full Text
- View/download PDF
48. Effect of exhaust gas recirculation composition on soot in ECN spray A conditions
- Author
-
Patel Chetankumar, Hespel Camille, Nguyen Tung Lam, Foucher Fabrice, and Mounaïm-Rousselle Christine
- Subjects
Chemical technology ,TP1-1185 ,Energy industries. Energy policy. Fuel trade ,HD9502-9502.5 - Abstract
Due to its strong impact on health, particulate matter is increasingly regulated by government emission standards for vehicles. As one of the sources of particulate matter is the soot produced by internal combustion engines, it remains a challenge to improve advanced combustion modes to reduce it. There is still, however, some lack of understanding about the formation and oxidation processes of soot, especially in “realistic” conditions, such as for example at high temperature and pressure conditions with or without the presence of exhaust gases. The objective of this study is to investigate soot formation in the case of n-Dodecane spray flames at conventional Diesel engine conditions generated in the New One Shot Engine by using diffused back-illumination extinction with different CO2 and water vapour contents. It was found that CO2 addition reduces the soot mass fraction if its volumetric concentration in ambient mixtures is at least 4.5% while 1% of water is sufficient to significantly reduce the soot mass fraction. The impact of the ambient mixture obtained in ECN spray A pre-burn vessels was also investigated to assess the accuracy against soot measurements available in the literature.
- Published
- 2020
- Full Text
- View/download PDF
49. Induced subgraph density. V. All paths approach Erdos-Hajnal
- Author
-
Nguyen, Tung, Scott, Alex, and Seymour, Paul
- Subjects
Mathematics - Combinatorics - Abstract
The Erd\H{o}s-Hajnal conjecture says that for every graph $H$, there exists $c>0$ such that every $H$-free graph $G$ has a clique or stable set of size at least $2^{c\log|G|}$ (a graph is ``$H$-free'' if no induced subgraph is isomorphic to $H$). The conjecture is known when $H$ is a path with at most four vertices, but remains open for longer paths. For the five-vertex path, Blanco and Buci\'c recently proved a bound of $2^{c(\log |G|)^{2/3}}$; for longer paths, the best existing bound is $2^{c(\log|G|\log\log|G|)^{1/2}}$. We prove a much stronger result: for any path $P$, every $P$-free graph $G$ has a clique or stable set of size at least $2^{(\log |G|)^{1-o(1)}}$. We strengthen this further, weakening the hypothesis that $G$ is $P$-free by a hypothesis that $G$ does not contain ``many'' copies of $P$, and strengthening the conclusion, replacing the large clique or stable set outcome with a ``near-polynomial'' version of Nikiforov's theorem.
- Published
- 2023
50. Fekete polynomials of principal Dirichlet characters
- Author
-
Chidambaram, Shiva, Mináč, Ján, Nguyen, Tung T., and Tân, Nguyen Duy
- Subjects
Mathematics - Number Theory - Abstract
Fekete polynomials associated to quadratic Dirichlet characters have interesting arithmetic properties, and have been studied in many works. In this paper, we study a seemingly simpler yet rich variant: the Fekete polynomial $F_n(x) = \sum_{a=1}^n \chi_n(a) x^a$ associated to a principal Dirichlet character $\chi_n$ of modulus $n$. We investigate the cyclotomic factors of $F_n$ and conjecturally describe all of them. One interesting observation from our computations is that the non-cyclotomic part $f_n$ of $F_n(x)/x$ seems to be always irreducible. We study this factor closely in the special case that $n$ is a product of two odd primes, proving separability in specific cases, and studying its coefficients and special values. Combining these theoretical results with computational evidence lets us identify the Galois group of $f_n$ for small $n$, and raises precise questions in general., Comment: Comments are welcome
- Published
- 2023
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