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Determining the degree of saturation of rocks as a function of time:A case study from mountainous area of Turkey

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Journal of Mountain Science 2018年第10期15卷 2307-2319页

作者： Serhat dag Department of Geological Engineering Gümüshane University 29100Turkey

The aim of this study is to scrutinize whether, in terms of saturation, the 48 hour duration suggested by ISRM(International Society for Rock Mechanics) methods and ASTM(American Society for Testing and Materials) standard in rocks is sufficient or not, and to examine how the degree of saturation of rocks may be determined as a function of time. For this purpose, samples from five different rock groups including igneous(andesite, granite, andesitic tuff) and sedimentary(limestone, sandstone) exposed in Gümü?hane city which is from mountainous area of north-eastern Turkey, have been compiled. Measurements were taken on the samples left for saturation under laboratory conditions as a result of which the degree of saturation values at the end of these time periods were determined. Similarly, at the end of 48 hours, the samples were left to dry under atmospheric conditions in the laboratory environment and their time dependent degree of saturation were also calculated at different times. The changes as a function of time in the degree of saturation were then examined mathematically using non-linear, exponential and logarithmic functions. Graphs and equations related with the acquired time-degree of saturation values and the correlation coefficient(r) values for these equalities have indicated a high accordance between time and degree of saturation for the studied rock groups. The applied methodology will be beneficial for determining the degree of saturation based on time for engineering studies that will be carried out in similar lithologies.

关键词： Degree of saturation Porosity Time Correlation coefficient

A simplified stability analysis method for LV inverter-based microgrids

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Journal of Modern Power Systems and Clean Energy 2019年第3期7卷 612-620页

作者： Bu lent dag MTimur AYDEMIR Space Technologies Research Institute TUBITAKAnkaraTurkey Gazi University Electrical and Electronics Engineering Department AnkaraTurkey

This paper presents a simplified small-signal stability analysis method for low voltage(LV) inverterbased microgrids, in a generalized manner. The simplification is based on a simplified microgrid structure that relies on dominating inverter coupling impedances with respect to interconnecting line impedances of LV distribution networks. The analysis is further simplified by analytically determining equilibrium points of system state variables in terms of known microgrid parameters. And it eliminates the additional analysis required for determination of the equilibrium points of the state variables. Simulation and analysis results show that the proposed method successfully predicts the instability boundaries of microgrid systems for resistive interconnecting lines.

关键词： Inverters Microgrids Stability analysis Droop control Distribution networks

Simulations of solitary waves of RLW equation by exponential B-spline Galerkin method

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Chinese Physics B 2017年第8期26卷 24-31页

作者： Melis Zorsahin Gorgulu Idris dag Dursun Irk Department of Mathematics-Computer Eskisehir Osmangazi University26480EskisehirTurkey Department of Computer Engineering Eskisehir Osmangazi University26480EskisehirTurkey

In this paper, an approximate function for the Galerkin method is composed using the combination of the exponential B-spline functions. Regularized long wave equation （RLW） is integrated fully by using an exponential B-spline Galerkin method in space together with Crank-Nicolson method in time. Three numerical examples related to propagation of sin- gle solitary wave, interaction of two solitary waves and wave generation are employed to illustrate the accuracy and the efficiency of the method. Obtained results are compared with some early studies.

关键词： solitary waves exponential B-spline Galerkin method RLW equation

Homogenization of a Class of Nonlinear Variational Inequalities with Applications in Fluid Film Flow

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Chinese Annals of Mathematics,Series B 2011年第3期32卷 417-434页

作者： dag LUKKASSEN Annette MEIDELL Peter WALL Narvik University College Department of Mathematics Lule University of Technology

The authors consider the homogenization of a class of nonlinear variational inequalities,which include rapid oscillations with respect to a *** homogenization of the corresponding class of differential equations is also *** results are applied to some models for the pressure in a thin fluid film fluid between two surfaces which are in relative *** is an important problem in the lubrication *** particular,the analysis includes the effects of surface roughness on both faces and the phenomenon of ***,the fluid can be modeled as Newtonian or non-Newtonian by using a Rabinowitsch fluid model.

关键词： Homogenization Two-scale convergence Lubrication Variational inequalities

The extended cubic B-spline algorithm for a modified regularized long wave equation

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Chinese Physics B 2013年第4期22卷 75-80页

作者： I.dag D.Irk M.SarI Faculty of Science and Arts Department of Mathematics and Computer Sciences Eskis ehir Osmangazi niversitesi Eskis ehir Turkey Faculty of Science and Arts Department of Mathematics Pamukkale niversitesi Denizli Turkey

A collocation method based on an extended cubic B-spline function is introduced for the numerical solution of the modified regularized long wave equation. The accuracy of the method is illustrated by studying the single solitary wave propagation and the interaction of two solitary waves of the modified regularized long wave equation.

关键词： collocation methods solitary waves

Lone Geniuses or One among Many?An Explorative Study of Contemporary Highly Cited Researchers

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Journal of Data and Information Science 2021年第2期6卷 41-66页

作者： dag W.Aksnes Kaare Aagaard Nordic Institute for Studies in Innovation Research and Education(NIFU) Oslo 0608Norway Danish Centre for Studies in Research&Research Policy Deptof Political Science&GovernmentMidtjylland 8000Denmark

Purpose:The ranking lists of highly cited researchers receive much public *** common interpretations,highly cited researchers are perceived to have made extraordinary contributions to ***,the metrics of highly cited researchers are often linked to notions of breakthroughs,scientific excellence,and lone ***/methodology/approach:In this study,we analyze a sample of individuals who appear on Clarivate Analytics’Highly Cited Researchers *** main purpose is to juxtapose the characteristics of their research performance against the claim that the list captures a small fraction of the researcher population that contributes disproportionately to extending the frontier and gaining—on behalf of society—knowledge and innovations that make the world healthier,richer,sustainable,and more ***:The study reveals that the highly cited articles of the selected individuals generally have a very large number of ***,these papers seldom represent individual contributions but rather are the result of large collective research efforts conducted in research *** challenges the common perception of highly cited researchers as individual geniuses who can be singled out for their extraordinary ***,the study indicates that a few of the individuals have not even contributed to highly cited original research but rather to reviews or clinical ***,the large number of authors of the papers implies that the ranking list is very sensitive to the specific method used for allocating papers and citations to *** the"whole count"methodology applied by Clarivate Analytics,each author gets full credit of the papers regardless of the number of additional *** study shows that the ranking list would look very different using an alternative fractionalised *** limitations:The study is based on a limited part of the total population of highly cited *** implica

关键词： Highly cited researchers Research excellence Big science Citation Nobel Prize

Activity and Stability of Rare Earth-Based Hydride Alloys as Catalysts of Hydrogen Absorption-Oxidation Reactions

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Journal of Rare Earths 2004年第6期22卷 871-874页

作者：应桃开高学平胡伟康 Noréus dag College of Biology and Chemistry Zhejiang Normal University Jinhua 321004China Institute of New Energy Material Chemistry Nankai University Tianjin 300071China Department of Structural Chemistry Arrhenius Laboratory Stockholm University S-106 91 Stockholm Sweden

Rare earth-based AB(5)-type hydrogen storage alloys as catalysts of hydrogen-diffusion electrodes for hydrogen absorption and oxidation reactions in alkaline fuel cells were investigated. It is demonstrated that the metahydride hydrogen-diffusion electrodes could be charged by hydrogen gas and electrochemically discharged, at the same time to retain a stable oxidation potential for a long period. The catalytic activities and stability are almost comparable with a Pt catalyst on the active carbon. Further improvement of performances is expected via reduction of catalyst size into nanometers.

关键词： inorganic chemistry electrocatalyst alkaline fuel cell hydrogen oxidation rare earths

Liver segment 2+3 living donation in liver transplantation for colorectal liver metastases

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Hepatobiliary Surgery and Nutrition 2020年第3期9卷 382-384页

作者： Svein Dueland Pal-dag Line Department of Oncology Oslo University HospitalOsloNorway Department of Transplantation Medicine Oslo University HospitalOsloNorway and Institute of Clinical MedicineUniversity of OsloNorway

Liver transplantation(LT)was offered to some colorectal cancer(CRC)patients with liver only metastases in the 1990s,however the treatment option was discontinued due to poor overall survival(OS)of 43%at 2 years posttr... 详细信息

关键词： colorectal metastases Liver

Global trends in international research collaboration, 1980-2021

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Journal of Data and Information Science 2023年第2期8卷 26-42页

作者： dag W.Aksnes Gunnar Sivertsen NIFU-Nordic Institute for studies in Innovation Research and EducationØkernveien 90653 OsloNorway

Purpose:The aim of this study is to analyze the evolution of international research collaboration from 1980 to *** study examines the main global patterns as well as those specific to individual countries,country groups,and different areas of ***/methodology/approach:The study is based on the Web of Science Core collection *** than 50 million publications are analyzed using co-authorship *** collaboration is defined as publications having authors affiliated with institutions located in more than one ***:At the global level,the share of publications representing international collaboration has gradually increased from 4.7%in 1980 to 25.7%in *** proportion of such publications within each country is higher and,in 2021,varied from less than 30%to more than 90%.There are notable disparities in the temporal trends,indicating that the process of internationalization has impacted countries in different *** factors such as country size,income level,and geopolitics may explain the *** limitations:Not all international research collaboration results in joint co-authored scientific *** co-authorship is a partial indicator of such *** limitation is that the applied full counting method does not take into account the number of authors representing in each country in the *** implications:The study provides global averages,indicators,and concepts that can provide a useful framework of reference for further comparative studies of international research ***/value:Long-term macro-level studies of international collaboration are rare,and as a novelty,this study includes an analysis by the World Bank’s division of countries into four income groups.

关键词： International collaboration Research collaboration Team science Co-authorship Internationalization Globalization