检索结果-内蒙古大学图书馆

arXiv 2022年

作者： Partin, Lauren Schiavazzi, Daniele E. Long, Carlos A. Sing Department Of Applied And Computational Mathematics And Statistics University Of Notre Dame Notre DameIN United States Institute For Mathematical And Computational Engineering Institute For Biological And Medical Engineering Pontificia Universidad Católica De Chile Santiago Chile ANID - Millennium Science Initiative Program Millennium Nucleus Center For The Discovery Of Structures In Complex Data Chile ANID - Millennium Science Initiative Program Millennium Nucleus Center For Cardiovascular Magnetic Resonance Chile

Novel Magnetic Resonance (MR) imaging modalities can quantify hemodynamics but require long acquisition times, precluding its widespread use for early diagnosis of cardiovascular disease. To reduce the acquisition times, reconstruction methods from undersampled measurements are routinely used, that leverage representations designed to increase image compressibility. Reconstructed anatomical and hemodynamic images may present visual artifacts. Although some of these artifact are essentially reconstruction errors, and thus a consequence of undersampling, others may be due to measurement noise or the random choice of the sampled frequencies. Said otherwise, a reconstructed image becomes a random variable, and both its bias and its covariance can lead to visual artifacts;the latter leads to spatial correlations that may be misconstrued for visual information. Although the nature of the former has been studied in the literature, the latter has not received as much attention. In this study, we investigate the theoretical properties of the random perturbations arising from the reconstruction process, and perform a number of numerical experiments on simulated and MR aortic flow. Our results show that the correlation length remains limited to two to three pixels when a Gaussian undersampling pattern is combined with recovery algorithms based on 1-norm minimization. However, the correlation length may increase significantly for other undersampling patterns, higher undersampling factors (i.e., 8× or 16× compression), and different reconstruction methods. © 2022, CC BY-NC-ND.

关键词： Magnetic resonance

来源：评论

学校读者我要写书评

暂无评论

Drivers of the World Tourism: A Regional View

SSRN

引用

SSRN 2023年

作者： Ventura, Rodrigo V. Fernandes, Elton Cabo, Manoela de Mello Carvalho, Carla F. Fernandes, Vicente Aprigliano COPPE Production Engineering Program UFRJ Federal University of Rio de Janeiro Rio de Janeiro Brazil COPPE Transportation Engineering Program UFRJ Federal University of Rio de Janeiro Rio de Janeiro Brazil IBGE Brazilian Institute of Geography and Statistics Rio de Janeiro Brazil Escuela de Ingeniería de Construcción y Transporte Pontificia Universidad Católica de Valparaíso Chile

The commercial air transport innovation and its technological evolution, especially after the Second World War, are fundamental factors in the people's movement growth between the nations of the planet. Advances in air transport and income growth have allowed more and more people to realise the dream of getting to know and interacting with cultures from other countries, most times very far from their places of residence. Many studies examine the travel demand evolution more broadly or specifically between locations, which we can characterise as tourist demand. The quest to understand the drivers that move people between different destinations on the planet is a fundamental element of the company's planning and for the public policies formulation. This study contributes to this sense, analysing three socioeconomic factors of the world reality: globalisation, the countries’ economic structure and this structure's dynamics. Using panel data regression analysis methodology and the World Bank's world development indicators, relationships between the international tourism evolution and the mentioned socioeconomic factors are estimated and discussed. Each of the three perspectives analysed shows a strong relationship with the historical demand for tourism. The globalisation indicator revealed a growing positive impact on the level of tourist movement. The country's economic structure indicator showed a significant difference between countries, which suggests the need to examine tourism according to regions concept. Among dynamics indicators, income was the major factor in the tourism indicators variation. © 2023, The Authors. All rights reserved.

关键词： Regression analysis

来源：评论

学校读者我要写书评

暂无评论

M2FN: Multi-step modality fusion for advertisement image assessment

arXiv

引用

arXiv 2021年

作者： Park, Kyung-Wha Ha, Jung-Woo Lee, JungHoon Kwon, Sunyoung Kim, Kyung-Min Zhang, Byoung-Tak Interdisciplinary Program in Neuroscience Seoul National University Korea Republic of NAVER AI LAB NAVER CLOVA Statistics and Actuarial Science Soongsil University Korea Republic of School of Biomedical Convergence Engineering Pusan National University Korea Republic of Department of Computer Science and Engineering Seoul National University Korea Republic of Surromind Robotics

Assessing advertisements, specifically on the basis of user preferences and ad quality, is crucial to the marketing industry. Although recent studies have attempted to use deep neural networks for this purpose, these studies have not utilized image-related auxiliary attributes, which include embedded text frequently found in ad images. We, therefore, investigated the influence of these attributes on ad image preferences. First, we analyzed large-scale real-world ad log data and, based on our findings, proposed a novel multi-step modality fusion network (M2FN) that determines advertising images likely to appeal to user preferences. Our method utilizes auxiliary attributes through multiple steps in the network, which include conditional batch normalization-based low-level fusion and attention-based high-level fusion. We verified M2FN on the AVA dataset, which is widely used for aesthetic image assessment, and then demonstrated that M2FN can achieve state-of-the-art performance in preference prediction using a real-world ad dataset with rich auxiliary attributes. © 2021, CC BY-NC-SA.

关键词： Marketing

来源：评论

学校读者我要写书评

暂无评论

Exploring Multiscale Quantum Media: High-Precision Efficient Numerical Solution of the Fractional Schrödinger equation, Eigenfunctions with Physical Potentials, and Fractionally-Enhanced Quantum Tunneling

arXiv

引用

arXiv 2024年

作者： Lewis, Joshua M. Carr, Lincoln D. Quantum Engineering Program Colorado School of Mines GoldenCO80401 United States Department of Physics Colorado School of Mines GoldenCO80401 United States Department of Applied Mathematics and Statistics Colorado School of Mines GoldenCO80401 United States

Fractional evolution equations lack generally accessible and well-converged codes excepting anomalous diffusion. A particular equation of strong interest to the growing intersection of applied mathematics and quantum information science and technology is the fractional Schrödinger equation, which describes sub-and super-dispersive behavior of quantum wavefunctions induced by multiscale media. We derive a computationally efficient sixth-order split-step numerical method to converge the eigenfunctions of the FSE to arbitrary numerical precision for arbitrary fractional order derivative. We demonstrate applications of this code to machine precision for classic quantum problems such as the finite well and harmonic oscillator, which take surprising twists due to the non-local nature of the fractional derivative. For example, the evanescent wave tails in the finite well take a Mittag-Leffer-like form which decay much slower than the well-known exponential from integer-order derivative wave theories, enhancing penetration into the barrier and therefore quantum tunneling rates. We call this effect fractionally enhanced quantum tunneling. This work includes an open source code for communities from quantum experimentalists to applied mathematicians to easily and efficiently explore the solutions of the fractional Schrödinger equation in a wide variety of practical potentials for potential realization in quantum tunneling enhancement and other quantum applications. © 2024, CC BY.

关键词： Eigenvalues and eigenfunctions

来源：评论

学校读者我要写书评

暂无评论

MG-GNN: Multigrid Graph Neural Networks for Learning Multilevel Domain Decomposition Methods

arXiv

引用

arXiv 2023年

作者： Taghibakhshi, Ali Nytko, Nicolas Zaman, Tareq Uz MacLachlan, Scott Olson, Luke N. West, Matthew Department of Mechanical Science and Engineering University of Illinois Urbana-Champaign United States Department of Computer Science University of Illinois Urbana-Champaign United States Scientific Computing Program Memorial University of Newfoundland Canada Department of Mathematics and Statistics Memorial University of Newfoundland Canada

Domain decomposition methods (DDMs) are popular solvers for discretized systems of partial differential equations (PDEs), with one-level and multilevel variants. These solvers rely on several algorithmic and mathematical parameters, prescribing overlap, subdomain boundary conditions, and other properties of the DDM. While some work has been done on optimizing these parameters, it has mostly focused on the one-level setting or special cases such as structured-grid discretizations with regular subdomain construction. In this paper, we propose multigrid graph neural networks (MG-GNN), a novel GNN architecture for learning optimized parameters in two-level DDMs. We train MG-GNN using a new unsupervised loss function, enabling effective training on small problems that yields robust performance on unstructured grids that are orders of magnitude larger than those in the training set. We show that MG-GNN outperforms popular hierarchical graph network architectures for this optimization and that our proposed loss function is critical to achieving this improved performance. © 2023, CC BY.

关键词： Domain decomposition methods

来源：评论

学校读者我要写书评

暂无评论

Discrete Fourier Transform Approximations Based on the Cooley-Tukey Radix-2 Algorithm

arXiv

引用

arXiv 2024年

作者： Coelho, D.F.G. Cintra, R.J. The Signal Processing Group Departamento de Estatística Brazil The Graduate Program in Electrical Engineering The Graduate Program in Statistics Universidade Federal de Pernambuco Recife Brazil The Signal Processing Group Departamento de Estatística Universidade Federal de Pernambuco Brazil Equipe Cairn IRISA-INRIA Université de Rennes Rennes France Lyon France

This report elaborates on approximations for the discrete Fourier transform by means of replacing the exact Cooley-Tukey algorithm twiddle-factors by low-complexity integers, such as 0,±1/2,±1. Copyright ... 详细信息

关键词： Discrete Fourier transforms

来源：评论

学校读者我要写书评

暂无评论

Correlations between student connectivity and academic performance: A pandemic follow-up

引用

Physical Review Physics Education Research 2023年第1期19卷 010106-010106页

作者： Nathan Crossette Lincoln D. Carr Bethany R. Wilcox Department of Physics University of Colorado Boulder Boulder Colorado 80309 USA Quantum Engineering Program Colorado School of Mines Golden Colorado 80401 USA Department of Physics Colorado School of Mines Golden Colorado 80401 USA Department of Applied Mathematics and Statistics Colorado School of Mines Golden Colorado 80401 USA

Social network analysis (SNA) has been gaining traction as a technique for quantitatively studying student collaboration. We analyze networks, constructed from student self-reports of collaboration on homework assignments, in two courses from the University of Colorado Boulder and one course from the Colorado School of Mines. All three courses occurred during the COVID-19 pandemic, which allows for a comparison between the course at the Colorado School of Mines (in a fully remote format) with results from a previous pre-pandemic study of student collaboration at the Colorado School of Mines (in an in-person format), as well as comparison between the Mines results with the two University of Colorado courses (in a hybrid format). We compute nodal centrality measures and calculate the correlation between student centrality and performance. Results varied widely between each of the courses studied. The course at the Colorado School of Mines had strong correlations between many centrality measures and performance which matched the patterns seen in the pre-pandemic study. The courses at the University of Colorado Boulder showed weaker correlations, and one course showed nearly no correlations at all between students’ connectivity to their classmates and their performance. Taken together, the results from the trio of courses indicate that the context and environment in which the course is situated play a more important role in fostering a correlation between student collaboration and course performance than the format (remote, hybrid, in-person) of the course, a finding which has implications for the broader use of SNA within physics education research. Additionally, we conducted a short study on the effect that missing nodes may have on the correlations calculated from the measured networks, an analysis largely missing from the SNA literature within PER. This investigation showed that missing nodes tend to shift correlations towards zero, providing evidence that the stati

关键词： Learning environment Research methodology Upper undergraduate students

来源：评论

学校读者我要写书评

暂无评论

Proposal for a unified selection to medical residency programs

引用

Revista da Associação Médica Brasileira (English Edition) 2013年第6期59卷 583-588页

作者： Sônia Ferreira Lopes Toffoli Olavo Franco Ferreira Filho Dalton Francisco de Andrade Graduate Program in Production Engineering Universidade Federal de Santa Catarina Florianópolis SC Brazil Universidade Estadual de Londrina Londrina PR Brazil Department of Internal Medicine Universidade Estadual de Londrina Londrina PR Brazil Department of Informatics and Statistics Universidade Federal de Santa Catarina Florianópolis SC Brazil

Objective This paper proposes the unification of entrance exams to medical residency programs (MRP) in Brazil. Problems related to MRP and its interface with public health problems in Brazil are highlighted and how this proposal is able to help solving these problems. Methods The proposal is to create a database to be applied in MRP unified exams. Some advantages of using the Item Response Theory (IRT) in this database are highlighted. Results The MRP entrance exams are developed and applied decentralized where each school is responsible for its examination. These exams quality are questionable. Reviews about items quality, validity and reliability of appliances are not common disclosed. Conclusion Evaluation is important in every education system bringing on required changes and control of teaching and learning. The proposal of MRP entrance exams unification, besides offering high quality exams to institutions participants, could be as an extra source to rate medical school and cause improvements, provide studies with a database and allow a regional mobility. Objetivo Este artigo propõe a unificação dos exames de acesso aos programas de Residência Médica (RM) no Brasil. São destacados problemas relacionados à RM e a sua interface com problemas da saúde pública no Brasil e como esta proposta pode auxiliar no enfrentamento desses problemas. Métodos A proposta consiste na criação de um banco de itens para ser aplicado na seleção unificada para a RM. São destacadas algumas vantagens em utilizar a Teoria de Resposta ao Item (TRI) nesse banco de itens. Resultados Os exames de seleção para os programas de RM são elaborados e aplicados de forma descentralizadas, cada instituição é responsável por sua avaliação. A qualidade dessas provas é questionável, os estudos referentes à qualidade dos itens, a validade e a confiabilidade dos instrumentos não são comumente divulgados. Conclusão A avaliação é importante em todo sistema de ensino, provocando transformações necessárias e

关键词： Medical residency Selection process Classical Test Theory Item Response Theory Residência médica Processo seletivo Teoria Clássica do Teste Teoria de Resposta ao Item

来源：评论

学校读者我要写书评

暂无评论

Model guided adaptive design and Analysis in computer experiment

引用

Statistical Analysis and Data Mining 2012年第5期5卷 399-409页

作者： Yu, Qingzhao Li, Bin Fang, Zhide Peng, Lu Biostatistics Program School of Public Health Louisiana State University Health Sciences Center New Orleans LA United States Department of Experimental Statistics Louisiana State University Baton Rouge LA United States Department of Electrical and Computer Engineering Louisiana State University Baton Rouge LA United States

Computer experiments have become increasingly important in several different industries. These experiments save resources by exploring different designs without necessitating real hardware manufacturing. However, computer experiments usually require lengthy simulation times and powerful computational capacity. Therefore, it is often pragmatically impossible to run experiments on a complete design space. In this paper, we propose an adaptive sampling scheme that interactively works with predictive models to sequentially select design points for computer experiments. The selected samples are used to build predictive models, which in turn guide further sampling and predict the entire design space. For illustration, we use Bayesian additive regression trees (BART), multiple additive regression trees (MART), treed Gaussian process and Gaussian process to guide the proposed sampling method. Both real data and simulation studies show that our sampling method is effective in that (i) it can be used with different predictive models;(ii) it can select multiple design points without repeatedly refitting the predictive models, which makes parallel simulations possible and (iii) the predictive model built on its generated samples gives more accurate predictions on the unsampled points than the models built on samples from other methods such as random sampling, space-filling designs and some adaptive sampling methods. © 2012 Wiley Periodicals, Inc.

关键词： Sampling

来源：评论

学校读者我要写书评

暂无评论

Clustering spatial on the GSTAR model for replacement new oil well

引用

AIP Conference Proceedings 2013年第1期1554卷 205-209页

作者： Budi Nurani Ruchjana Atje Setiawan Abdullah Toni Toharudin I Gede Nyoman Mindra Jaya Department of Mathematics Faculty of Mathematics and Natural Sciences Universitas Padjadjaran Indonesia Informatics Engineering Study Program Faculty of Mathematics and Natural Sciences Universitas Padjadjaran Indonesia Department of Statistics Faculty of Mathematics and Natural Sciences Universitas Padjadjaran Jl Raya Bandung Sumedang Km 21 Jatinangor Sumedang 45363-West Java Indonesia

Space time models such as the Generalized Space Time Autoregressive (GSTAR) is an important theoretical research topics with many applications in large number of areas ranging from the spread of diseases, mining, economic growth, ecology, agriculture and population development. In this paper we introduce a clustering spatial for determining a group of locations for weight matrix of the GSTAR model. We use Ordinary Least Squares method to estimate the parameters of model and apply the result to develop a GSTAR-Kriging model for replacement new oil wells at volcanic field in Jatibarang, West Java-Indonesia.

关键词：

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：