检索结果-南通市图书馆

Iterative Subregion Correction Preconditioners with Adaptive Tolerance for Problems with Geometrically Localized Stiffness

引用

Communications on Applied Mathematics and Computation 2024年第2期6卷 811-836页

作者： Michael Franco per-Olof persson Will Pazner Department of Mathematics University of CaliforniaBerkeleyBerkeleyCA 94720-3840USA Fariborz Maseeh Department of Mathematics and Statistics Portland State UniversityPortlandOR 97201USA

We present a class of preconditioners for the linear systems resulting from a finite element or discontinuous Galerkin discretizations of advection-dominated *** preconditioners are designed to treat the case of geometrically localized stiffness,where the convergence rates of iterative methods are degraded in a localized subregion of the *** convergence may be caused by a number of factors,including the mesh size,anisotropy,highly variable coefficients,and more challenging *** approach taken in this work is to correct well-known preconditioners such as the block Jacobi and the block incomplete LU(ILU)with an adaptive inner subregion *** goal of these preconditioners is to reduce the number of costly global iterations by accelerating the convergence in the stiff region by iterating on the less expensive reduced *** tolerance for the inner iteration is adaptively chosen to minimize subregion-local work while guaranteeing global convergence *** present analysis showing that the convergence of these preconditioners,even when combined with an adaptively selected tolerance,is independent of discretization parameters(e.g.,the mesh size and diffusion coefficient)in the *** demonstrate significant performance improvements over black-box preconditioners when applied to several model convection-diffusion ***,we present performance results of several variations of iterative subregion correction preconditioners applied to the Reynolds number 2.25×10^(6)fluid flow over the NACA 0012 airfoil,as well as massively separated flow at 30°angle of attack.

关键词： Subregion correction Nested Krylov Geometrically localized stiffness

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

BOUNDARY PROCEDURES FOR THE TIME-DEPENDENT BURGERS' EQUATION UNDER UNCERTAINTY

引用

Acta Mathematica Scientia 2010年第2期30卷 539-550页

作者： per Pettersson Jan Nordstrm Gianluca Iaccarino Mechanical Engineering and Institute for Computational Mathematical Engineering Stanford University Division of Scientific Computing Department of Information TechnologyUppsala University School of Mechanical Industrial and Aeronautical EngineeringUniversity of the Witvatersrand Department of Aeronautics and Systems Integration FOIThe Swedish Defense Research Agency

The Burgers＇ equation with uncertain initial and boundary conditions is approximated using a Polynomial Chaos Expansion （PCE） approach where the solution is represented as a series of stochastic, orthogonal polynomials. The resulting truncated PCE system is solved using a novel numerical discretization method based on spatial derivative operators satisfying the summation by parts property and weak boundary conditions to ensure stability. The resulting PCE solution yields an accurate quantitative description of the stochastic evolution of the system, provided that appropriate boundary conditions are available. The specification of the boundary data is shown to influence the solution; we will discuss the problematic implications of the lack of precisely characterized boundary data and possible ways of imposing stable and accurate boundary conditions.

关键词： stochastic Burgers' equation uncertainty quantification polynomial chaos

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

An Institutional Model for Collaborative Disaster Risk Management in the Southern African Development Community(SADC) Region

引用

International Journal of Disaster Risk Science 2016年第4期7卷 343-352页

作者： Mmaphaka Tau Dewald van Niekerk per Becker African Centre for Disaster Studies North-West University Division of Risk Management and Societal Resilience Lund University

This article presents and argues for a collaborative model for disaster risk management in the Southern African Development Community(SADC).The research employed a qualitative study through a literature review and empirical research through focus group interviews to realize its *** a key theory of multinational collaboration,neoliberal institutionalism—a subset of the international relations theory—was used to develop the SADC institutional collaborative *** model combined the theoretical,political,and technical dimensions of collaboration to enhance buy-in for the disaster risk management and reduction function of *** model demonstrates the need for a multidisciplinary approach to achieving disaster risk management and reduction in the SADC and elsewhere,if the developmental objectives of disaster risk reduction are to be realized without interference in the domestic affairs of the member *** model is therefore grounded in seeking consensus and cooperation among cooperating states in a quest to ensure national implementation of the regional framework on disaster risk reduction.

关键词： Disaster risk management Disaster risk reduction International relations Neoliberal institutionalism Southern African Development Community(SADC)

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Laparoscopic distal pancreatectomy for adenocarcinoma of the pancreas

引用

World Journal of Gastroenterology 2014年第37期20卷 13402-13411页

作者： Bergthor Bjrnsson per Sandstrm Department of Surgery County Council of stergtland and Department of Clinical and Experimental MedicineFaculty of Health SciencesLinkping University

Since the first report on laparoscopic distal pancreatectomy (LDP) appeared in the 1990s, the procedure has been performed increasingly frequently to treat both benign and malignant lesions of the pancreas. Many earlier publications have shown LDP to be a good alternative to open distal pancreatectomy for benign lesions, although this has never been studied in a prospective, randomized manner. The evidence for the use of LDP to treat adenocarcinoma of the pancreas is not as well established. The purpose of this review is to evaluate the current evidence for LDP in cases of pancreatic adenocarcinoma. We conducted a review of English language publications reporting LDP results between 1990 and 2013. All studies reporting results in patients with histologically proven pancreatic adenocarcinoma were included. Thirty-nine publications were found and included in the results for a total of 309 cases of pancreatic adenocarcinoma (potential double publications were not eliminated). Most LDP procedures are performed in selected cases and generally involve smaller tumors than open distal pancreatectomy (ODP) procedures. Some of the papers report unselected cases and include procedures on larger tumors. The number of lymph nodes harvested using LDP is comparable to the number obtained with ODP, as is the frequency of R0 resections. Current data suggest that similar short term oncological results can be obtained using LDP as those obtained using ODP.

关键词： Adenocarcinoma of the pancreas Laparoscopy Distal pancreatectomy Surgical margins Pancreatic resection

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Intermittent androgen deprivation therapy in patients with prostate cancer: Connecting the dots

引用

Asian Journal of Urology 2017年第4期4卷 208-222页

作者： per-Anders Abrahamsson Department of Urology Skane University HospitalLund UniversityMalmooSweden

Intermittent androgen deprivation therapy(IADT)is now being increasingly opted by the treating physicians and patients with prostate *** most common reason driving this is the availability of an off-treatment period to the patients that provides some relief from treatment-related side-effects,and reduced treatment *** may also delay the progression to castration-resistant prostate ***,the use of IADT in the setting of prostate cancer has not been strongly substantiated by data from clinical *** factors seem to contribute towards this inadequacy of supportive data for the use of IADT in patients with prostate cancer,e.g.,population characteristics(both demographic and clinical),study design,treatment regimen,on-and off-treatment criteria,duration of active treatment,endpoints,and *** present review article focuses on seven clinical trials that evaluated the efficacy of IADT *** androgen deprivation therapy for the treatment of prostate *** results from these clinical trials have been discussed in light of the factors that may impact the treatment outcomes,especially the disease(tumor)*** on evidence,potential candidate population for IADT has been suggested along with recommendations for the use of IADT in patients with prostate cancer.

关键词： Continuous androgen deprivation therapy Intermittent androgen deprivation therapy Prostate cancer Study designs and outcomes Tumor burden

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Gap characteristics and their effects on regeneration,dominance and early growth of woody species

引用

Journal of Plant Ecology 2009年第1期2卷 21-29页

作者： Indra Prasad Sapkota per Christer Oden Swedish University of Agricultural Sciences Southern Swedish Forest Research CentreTropical Silviculture and Seed Science GroupPO Box 49SE-23053 AlnarpSweden

Aims We aim to examine the canopy gap characteristics and evaluate their influence on regeneration,dominance and the early growth of woody species in seasonally dry Shorea robusta forests(Sal forests).Methods Sixty canopy gaps were surveyed in six randomly located transects belts in seasonally dry subtropical Sal forests of central *** transect belt was followed until 10 gap sites were *** equation for the area of an ellipse was used to calculate the size of canopy gap,measuring the longest axis and its perpendicular shorter ***,sizes,ages and causes of tree falls creating canopy gaps along with number and sizes of border trees were identified and *** gap inventories were carried out using square 25-m2 quadrats placed in the middle of each *** individuals>2 m in height within the quadrat were identified at the species level and their diameter at breast height was *** assigned a nested 4-m2 quadrat to the corner of each 25-m2 quadrat,within which all woody individuals>10 cm tall were identified at the species level,and counted them and their regeneration mechanisms were *** height and collar diameter of the tallest individuals were *** statistics was calculated for the variables of interests and Pearson correlation,linear regression,independent-sample t-test and chi-square test were used to relate them and to test for their *** Findings The study found mean gap size of 283 m2 and;50%gaps of 10–15 years *** created by natural single-tree falls were significantly more numerous,and their mean size was significantly smaller than those resulting from artificial causes or multiple-tree *** size correlated with the basal area of felled trees,but it did not correlate with the number of tree *** tree fall basal area was significantly positively correlated to the seed-originated seedling to resprout ratio,it was negatively correlated,along with gap area and th

关键词： canopy gap seedling density seedling growth basal area Sal forests Nepal

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Study of performance on Recharging the Borehole by Means of Exhaust-air Energy

引用

Journal of Donghua University(English Edition) 2009年第2期26卷 126-131页

作者：周亚素 FAHLN per School of Environmental Science and Engineering Donghua University Chalmers University of Technology

In this paper,the performance analysis of recharging the borehole by means of exhaust-air energy is carried *** results show that a vertical borehole used as heat source for a Ground Source Heat Pump(GSHP)can be recharged in high *** equal heat transfer capabilities of exhaust-air coil and borehole collector,the system provides a maximum overall ***,due to ground infinite capacity,the optimum brine flow rate is different from conventional two-exchanger *** recharging system provides two peak overall efficiencies when the capacity ratio Cr=5 for laminar flow and Cr=15 for turbulent flow *** overall efficiency is independent of exhaust-air temperature and undisturbed ground temperature,although the fluid properties depend on *** practical system lower ethyl percentage brine should be chosen if the freezing point meets the system request,which can provide a higher overall efficiency.

关键词： recharging borehole exhaust-air coil brine flowrate coil allocation ratio efficiency mathematical model

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Saussure’s Prolegomena——Toward a Semiotics of the Mind

引用

Language and Semiotic Studies 2022年第1期8卷 91-104页

作者： per Aage Brandt 不详

The study of language is based either on the word or on the sentence as basic *** de Saussure opted for the word;other linguists later preferred the sentence or chose to ignore the difference between word and ***,however,have extra-linguistic functions related to the topologies of thought,the spontaneous geometrical imageries of meaningful mental figuration,as we know them from sign posts,from verbal descriptions,and from the semiotics of *** words,rather than sentences,are in this sense the essential connectors of language and thought,then the general architecture of linguistic structures,including semantics and syntax,should be centered around this lexical“window”into the thinking mind,and the semiotic modes of language and signs may then be described by similar architectures directly connected to the figurative mind *** paper offers tentative connected models of the architectures of language,signs,and the figurative mind,and suggests the possibility of interpreting Ferdinand de Saussure’s semiological intuitions in the sense of a semiotics of the mind along these cognitive-semiotic lines.

关键词： word-based linguistics mental architecture cognitive semiotics sign categories

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

The Meaning and Madness of Money: A Semio-Ecological Analysis

引用

Language and Semiotic Studies 2017年第3期3卷 1-25页

作者： per Aage Brandt Case Western Reserve University

In this paper, I propose an overall model of the semantic and semiotic functions of money and capital forms, based on an ecological view of human activity and a theory of the origin of money(coined precious metals). The meaning of money is replaced in a structured human perspective, and a critical discussion is outlined on the grounds of the material and capital flows and functions identified. The madness of money follows from the separation of economy and ecology. That madness causes serious damage, especially under certain circumstances that the structural analysis can identify. Finally I add some new considerations on the psycho-semiotic implications of the analysis. The societal structure discussed can be interpreted in terms that have strikingly direct correspondence to those describing semiotic aspects of language and the human psyché, where the concepts of meaning and madness are immediately pertinent.

关键词： semio-ecology money origins socio-semiotics the money sign the symbolic order

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Bile spillage should be avoided in elective cholecystectomy

引用

Hepatobiliary Surgery and Nutrition 2019年第6期8卷 640-642页

作者： per Sandstrom Bergthor Bjornsson Department of Surgery University Hospital of LinkopingLinkopingSweden Department of Clinical and Experimental Medicine University Hospital of LinkopingLinkopingSweden

We read with great interest the article entitled"Adverse Outcomes After Bile Spillage in Incidental Gallbladder Cancers:A Population-based Study"by Michael *** et al.,which was e-published the 13th of April,2019 in Annals of Surgery(1).This retrospective study was conducted by the University of Calgary and included all cholecystectomies performed from 2001-2015 in the region of Alberta,*** aim of the study was to evaluate if bile spillage during the index operation for presumed benign gallstone disease would affect survival in the group of patients found to have incidental gallbladder cancer.

关键词： Canada Surgery gallbladder

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

欢迎您,

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

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

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

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

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：