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problems

第二课堂(A) 2016年第4期 28-29页

作者：梁闻云

Hello,everyone.Let’s have a discussion about problems.These days we often have a lot of worries.Don’t worry.problems and worries are normal in life.My friend Krystal has a problem with her relationship.Why?She is a ... 详细信息

关键词： problems

On the use of 1g physical models for ground movements and soil-structure interaction problems

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Journal of Rock Mechanics and Geotechnical Engineering 2020年第1期12卷 197-211页

作者： Marwan Al Heib Fabrice Emeriault Huu-Luyen Nghiem INERIS Parc technologique AlataVemeuil-En-HalatteF-60550France Universite Grenoble Alpes 3SRGrenobleF-38000France CNRS 3SRGrenobleF-38000France

The paper focusses on the use of physical modelling in ground movements(induced by underground cavity collapse or mining/tunnelling)and associated soil-structure interaction issues.The paper presents first an overview of using 1 g physical models to solve geotechnical problems and soil-structure interactions related to vertical ground movements.Then the lg physical modelling application is illustrated to study the development of damage in masonry structure due to subsidence and cavity collapse.A largescale 1 g physical model with a 6 m^3 container and 15 electric jacks is presented with the use of a threedimensional(3D)image correlation technique.The influence of structure position on the subsidence trough is analysed in terms of crack density and damage level.The obtained results can improve the methodology and practice for evaluation of damage in masonry structures.Nevertheless,ideal physical model is difficult to achieve.Thus,future improvement of physical models(analogue materials and instrumentation)could provide new opportunities for using 1 g physical models in geotechnical and soilstructure applications and research projects.

关键词： Subsidence Physical modelling Geotechnical problems Soil-structure interaction

TLBO with variable weights applied to shop scheduling problems

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CAAI Transactions on Intelligence Technology 2019年第3期4卷 148-158页

作者： Leonardo Ramos Rodrigues Joao Paulo Pordeus Gomes Electronics Division Institute of Aeronautics and SpacePraca Marechal Eduardo Gomes50Sao Josedos Campos 12228-904Brazil Computer Science Department Federal University of CearaRua Campus do PiciSnFortaleza 60440-554Brazil

The teaching–learning-based optimisation (TLBO) algorithm is a population-based metaheuristic inspired on the teaching–learning process observed in a classroom. It has been successfully used in a wide range of applications. In this study, the authors present a variant version of TLBO. In the proposed version, different weights are assigned to students during the student phase, with higher weights being assigned to students with better solutions. Three different approaches to assign weights are investigated. Numerical experiments with benchmark instances of the flow-shop and the job-shop scheduling problems are carried out to investigate the performance of the proposed approaches. They compare the proposed approaches with the original TLBO algorithm and with two variants of TLBOs proposed in the literature in terms of solution quality, convergence speed and simulation time. The results obtained by the application of a Friedman statistical test showed that the proposed approaches outperformed the original version of TLBO in terms of convergence, with no significant losses in the average makespan. The additional simulation time required by the proposed approaches is small. The best performance was achieved with the approach of assigning a fixed weight to half the students with the best solutions and assigning zero to other students.

关键词： TLBO variable weights shop scheduling problems

IMPROVED RELAXED POSITIVE-DEFINITE AND SKEW-HERMITIAN SPLITTING PRECONDITIONERS FOR SADDLE POINT problems

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Journal of Computational Mathematics 2019年第1期37卷 95-111页

作者： Yang Cao Zhiru Ren Linquan Yao School of Transportation Nantong UniversityNantong 226019China School of Statistics and Mathematics Central University of Finance and Economics Beijing 100081China School of Urban Rail Transportation Soochow UniversitySuzhou 215006China

We establish a class of improved relaxed positive-definite and skew-Hermitian splitting (IRPSS)preconditioners for saddle point problems.These preconditioners are easier to be implemented than the relaxed positive-definite and skew-Hermitian splitting (RPSS) preconditioner at each step for solving the saddle point problem.We study spectral properties and the minimal polynomial of the IRPSS preconditioned saddle point matrix.A theoretical optimal IRPSS preconditioner is also obtained,Numerical results show that our proposed IRPSS preconditioners are convergence rate of the GMRES method superior to the existing ones in accelerating the for solving saddle point problems.

关键词： Saddle point problems Preconditioning RPSS preconditioner Eigenvalues Krylov subspace method

AN UNFITTED hp-INTERFACE PENALTY FINITE ELEMENT METHOD FOR ELLIPTIC INTERFACE problems

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Journal of Computational Mathematics 2019年第3期37卷 316-339页

作者： Haijun Wu Yuanming Xiao Department of Mathematics Nanjing UniversityNanjing 210093China

An hp version of interface penalty finite element method(hp-IPFEM)is proposed to solve the elliptic interface problems in two and three dimensions on unfitted meshes.Error estimates in broken H1 norm,which are optimal with respect to h and suboptimal with respect to p by half an order of p,are derived.Both symmetric and non-symmetric IPFEM are considered.Error estimates in L^2 norm are proved by the duality argument.All the estimates are independent of the location of the interface relative to the meshes.Numerical examples are provided to illustrate the performance of the method.This paper is adapted from the work originally post on *** by the same authors(arXiv:1007.2893v1).

关键词： Elliptic interface problems Unfitted mesh hp-IPFEM

Use of‘T-tube’enterostomy in the management of emergency neonatal intestinal problems:a case series

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World Journal of Pediatric Surgery 2020年第4期3卷 30-33页

作者： Fazal Nouman Wahid Abdelbasit E Ali Department of Pediatric Surgery King Saud Medical CityRiyadhSaudi Arabia

Emergency neonatal intestinal problems,such as necrotizing enterocolitis(NEC),spontaneous intestinal perforation(SIP),intestinal atresia,meconium cyst and meco-nium ileus,pose serious challenges for pedi-atric surgeons and neonatologists.Stoma creation and primary anastomosis have been used for decades with various advantages and disadvantages of each approach.

关键词： neonatal anastomosis problems

Health problems among street children seeking care in the Center for Social and Preventive Medicine in Egypt

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World Journal of Pediatrics 2017年第5期13卷 503-507页

作者： Hoda Ibrahim Rizk Nihal Mohamed El Rifai Hana Mohamed Aboulghar Public Health and Community Medicine Department Faculty of MedicineCairo UniversityCairoEgypt Pediatrics Department Faculty of MedicineCairo UniversityCairoEgypt

Background:In Egypt,around 1 million children are on the streets.Street children's health is an issue that is not well researched.The objective of the current study was to determine the health problems of a targeted group of street children seeking medical care and to generate a hypothesis about the positive/negative role of street children care organizations.Methods:A cross-sectional study was done on 2169 street children who sought medical care at El-Basma clinic at the Center for Social and Preventive Medicine in Cairo University Children Hospital from January 2011 to July 2014.Results:Respiratory illnesses and skin problems were the most prevalent conditions,affecting 485 (22.4%) and 359 (16.6%) of the patients,respectively.Psychological issues and trauma were significantly higher among the adolescent group.Respiratory and gastrointestinal problems were significantly higher among children aged less than 2 years.Genital and cardiac problems were significantly higher among those referred from organizations whereas trauma was significantly higher among those coming directly from the streets.A significant proportion of children at the extremes of the studied age spectrum were coming directly from the streets.Sexually transmitted infections were rare problems.Conclusions:Respiratory and skin diseases were the major morbidity problems among street children,especially adolescent males.Organizations afforded opportunities for access to different health care services.

关键词： Egypt health problems street children

Fast Bayesian optimization of Needle-in-a-Haystack problems using zooming memory-based initialization (ZoMBI)

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npj Computational Materials 2023年第1期9卷 1543-1555页

作者： Alexander E.Siemenn Zekun Ren Qianxiao Li Tonio Buonassisi Department of Mechanical Engineering Massachusetts Institute of TechnologyCambridgeMAUSA Department of Electrical and Computer Engineering Singapore-MIT Alliance for Research and TechnologySingaporeSingapore Xinterra SingaporeSingapore Department of Mathematics National University of SingaporeSingaporeSingapore Institute for Functional Intelligent Materials National University of SingaporeSingaporeSingapore

Needle-in-a-Haystack problems exist across a wide range of applications including rare disease prediction,ecological resource management,fraud detection,and material property optimization.A Needle-in-a-Haystack problem arises when there is an extreme imbalance of optimum conditions relative to the size of the dataset.However,current state-of-the-art optimization algorithms are not designed with the capabilities to find solutions to these challenging multidimensional Needle-in-a-Haystack problems,resulting in slow convergence or pigeonholing into a local minimum.In this paper,we present a Zooming Memory-Based Initialization algorithm,entitled ZoMBI,that builds on conventional Bayesian optimization principles to quickly and efficiently optimize Needle-in-a-Haystack problems in both less time and fewer experiments.The ZoMBI algorithm demonstrates compute time speed-ups of 400×compared to traditional Bayesian optimization as well as efficiently discovering optima in under 100 experiments that are up to 3×more highly optimized than those discovered by similar methods.

关键词： optimization problems extreme

INTERIOR ESTIMATES OF SEMIDISCRETE FINITE ELEMENT METHODS FOR PARABOLIC problems WITH DISTRIBUTIONAL DATA

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Journal of Computational Mathematics 2019年第4期37卷 458-474页

作者： Li Guo Hengguang Li Yang Yang School of Data and Computer Science Sun Yat-Sen University Guangzhou 510275 China Department of Mathematics Wayne State University Michigan 48202 USA Department of Mathematical Sciences Michigan Technological University Michigan USA

Let Ω CR^d,1≤d≤3, be a bounded d-polytope. Consider the parabolic equation on Q with the Dirac delta function on the right hand side. We study the well-posedness, regularity, and the interior error estimate of semidiscrete finite element approximations of the equation. In particular, we derive that the interior error is bounded by the best local approximation error, the negative norms of the error, and the negative norms of the time derivative of the error. This result implies different convergence rates for the numerical solution in different interior regions, especially when the region is close to the singular point. Numerical test results are reported to support the theoretical prediction.

关键词： Parabolic problems Dist ributional data Finite element met hods Interior estimates Well-posedness Singularity