bluuebunny/crossref_metadata_2025_split huggingface dataset:
Coloring Geographical Threshold Graphs
Authors: Bradonjic Milan , Mueller Tobias , Percus Allon G. 
Published: August 2021

Graphs and Algorithms
We propose a coloring algorithm for sparse random graphs generated by the geographical threshold graph (GTG) model, a generalization of random geometric graphs (RGG). In a GTG, nodes are distributed in a Euclidean space, and edges are assigned according to a threshold function involving the distance between nodes as well as randomly chosen node weights. The motivation for analyzing this model is that many real networks (e. g., wireless networks, the Internet, etc.) need to be studied by using a ''richer'' stochastic model (which in this case includes both a distance between nodes and weights on the nodes). Here, we analyze the GTG coloring algorithm together with the graph's clique number, showing formally that in spite of the differences in structure between GTG and RGG, the asymptotic behavior of the chromatic number is identical: chi = ln n/ln ln n(1 +o(1)). Finally, we consider the leading corrections to this expression, again using the coloring algorithm and clique number to provide bounds on the chromatic number. We show that the gap between the lower and upper bound is within C ln n/(ln ln n)(2), and specify the constant C.
Separating the k-party communication complexity hierarchy: an application of the Zarankiewicz problem
Authors: Hayes Thomas P. 
Published: August 2021

special issue in honor of Laci Babai's 60th birthday: Combinatorics, Groups, Algorithms, and Complexity
For every positive integer k, we construct an explicit family of functions f : \0, 1\(n) -\textgreater \0, 1\ which has (k + 1) - party communication complexity O(k) under every partition of the input bits into k + 1 parts of equal size, and k-party communication complexity Omega (n/k(4)2(k)) under every partition of the input bits into k parts. This improves an earlier hierarchy theorem due to V. Grolmusz. Our construction relies on known explicit constructions for a famous open problem of K. Zarankiewicz, namely, to find the maximum number of edges in a graph on n vertices that does not contain K-s,K-t as a subgraph.
On the number of factors in codings of three interval exchange
Authors: Ambrož Petr , Frid Anna , Masáková Zuzana , Pelantová Edita 
Published: August 2021

Graph Theory
We consider exchange of three intervals with permutation (3, 2, 1). The aim of this paper is to count the cardinality of the set 3iet (N) of all words of length N which appear as factors in infinite words coding such transformations. We use the strong relation of 3iet words and words coding exchange of two intervals, i.e., Sturmian words. The known asymptotic formula #2iet(N)/N-3 similar to 1/pi(2) for the number of Sturmian factors allows us to find bounds 1/3 pi(2) +o(1) \textless= #3iet(N)N-4 \textless= 2 pi(2) + o(1)
8-star-choosability of a graph with maximum average degree less than 3
Authors: Chen Min , Raspaud André , Wang Weifan 
Published: August 2021

Graphs and Algorithms
A proper vertex coloring of a graphGis called a star-coloring if there is no path on four vertices assigned to two colors. The graph G is L-star-colorable if for a given list assignment L there is a star-coloring c such that c(v) epsilon L(v). If G is L-star-colorable for any list assignment L with vertical bar L(v)vertical bar \textgreater= k for all v epsilon V(G), then G is called k-star-choosable. The star list chromatic number of G, denoted by X-s(l)(G), is the smallest integer k such that G is k-star-choosable. In this article, we prove that every graph G with maximum average degree less than 3 is 8-star-choosable. This extends a result that planar graphs of girth at least 6 are 8-star-choosable [A. Kundgen, C. Timmons, Star coloring planar graphs from small lists, J. Graph Theory, 63(4): 324-337, 2010].
Optimal Computer Crash Performance Precaution
Authors: Laksman Efraim , Lennerstad Hakan , Lundberg Lars 
Published: August 2021

Distributed Computing and Networking
For a parallel computer system with m identical computers, we study optimal performance precaution for one possible computer crash. We want to calculate the cost of crash precaution in the case of no crash. We thus define a tolerance level r meaning that we only tolerate that the completion time of a parallel program after a crash is at most a factor r + 1 larger than if we use optimal allocation on m - 1 computers. This is an r-dependent restriction of the set of allocations of a program. Then, what is the worst-case ratio of the optimal r-dependent completion time in the case of no crash and the unrestricted optimal completion time of the same parallel program? We denote the maximal ratio of completion times f(r, m) - i.e., the ratio for worst-case programs. In the paper we establish upper and lower bounds of the worst-case cost function f (r, m) and characterize worst-case programs.
On-line ranking of split graphs
Authors: Borowiecki Piotr , Dereniowski Dariusz 
Published: August 2021

Graphs and Algorithms
A vertex ranking of a graph G is an assignment of positive integers (colors) to the vertices of G such that each path connecting two vertices of the same color contains a vertex of a higher color. Our main goal is to find a vertex ranking using as few colors as possible. Considering on-line algorithms for vertex ranking of split graphs, we prove that the worst case ratio of the number of colors used by any on-line ranking algorithm and the number of colors used in an optimal off-line solution may be arbitrarily large. This negative result motivates us to investigate semi on-line algorithms, where a split graph is presented on-line but its clique number is given in advance. We prove that there does not exist a (2-ɛ)-competitive semi on-line algorithm of this type. Finally, a 2-competitive semi on-line algorithm is given.
A note on contracting claw-free graphs
Authors: Fiala Jiří , Kamiński Marcin , Paulusma Daniël 
Published: August 2021

Discrete Algorithms
A graph containment problem is to decide whether one graph called the host graph can be modified into some other graph called the target graph by using a number of specified graph operations. We consider edge deletions, edge contractions, vertex deletions and vertex dissolutions as possible graph operations permitted. By allowing any combination of these four operations we capture the following problems: testing on (induced) minors, (induced) topological minors, (induced) subgraphs, (induced) spanning subgraphs, dissolutions and contractions. We show that these problems stay NP-complete even when the host and target belong to the class of line graphs, which form a subclass of the class of claw-free graphs, i.e., graphs with no induced 4-vertex star. A natural question is to study the computational complexity of these problems if the target graph is assumed to be fixed. We show that these problems may become computationally easier when the host graphs are restricted to be claw-free. In particular we consider the problems that are to test whether a given host graph contains a fixed target graph as a contraction.
Counting quadrant walks via Tutte's invariant method (extended abstract)
Authors: Bernardi Olivier , Bousquet-Mélou Mireille , Raschel Kilian 
Published: August 2021

Extended abstract presented at the conference FPSAC 2016, Vancouver.
In the 1970s, Tutte developed a clever algebraic approach, based on certain " invariants " , to solve a functional equation that arises in the enumeration of properly colored triangulations. The enumeration of plane lattice walks confined to the first quadrant is governed by similar equations, and has led in the past decade to a rich collection of attractive results dealing with the nature (algebraic, D-finite or not) of the associated generating function, depending on the set of allowed steps. We first adapt Tutte's approach to prove (or reprove) the algebraicity of all quadrant models known or conjectured to be algebraic (with one small exception). This includes Gessel's famous model, and the first proof ever found for one model with weighted steps. To be applicable, the method requires the existence of two rational functions called invariant and decoupling function respectively. When they exist, algebraicity comes out (almost) automatically. Then, we move to an analytic viewpoint which has already proved very powerful, leading in particular to integral expressions of the generating function in the non-D-finite cases, as well as to proofs of non-D-finiteness. We develop in this context a weaker notion of invariant. Now all quadrant models have invariants, and for those that have in addition a decoupling function, we obtain integral-free expressions of the generating function, and a proof that this series is differentially algebraic (that is, satisfies a non-linear differential equation).
Analysis of 300 Total Laparoscopic Hysterectomy Cases Performed by The Same Surgeon
Authors: Tamburacı Esra , Mulayim Barış 
Published: August 2021

Aim: This study aimed to evaluate the results of 300 cases of total laparoscopic hysterectomy (TLH) performed by the same surgeon.
Material and methods: During the study period, a total of 300 TLH operations were performed between January 2017 and December 2018. Demographic characteristics, indications of hysterectomy, uterine weights, intra-operative and post-operative complications, duration of the operation, length of hospital stay, blood loss of patients, visual analogue scores and amount of analgesics needed were retrospectively evaluated. Complications were analysed and compared with literature.
Results: Parameters analysed for 300 patients included in the study were as follows: mean age 47.82 ± 6.18 years, mean parity 3.4 ± 2.0 (0–11), BMI 27.41 ± 4.36 (kg/m²), mean uterine weight 367.67 ± 266.21 g (50–1600 g), mean operative time 89.07 ± 37.94 min (30–240 min), mean hospital stay 54.37 ± 21.95 h (24–168 h) and total complication rate 28 (9.3%). Conversion to open surgery was required in 29 (9.7%) patients. The level of technical difficulty and existence of prior abdominal surgery were associated with a higher risk of complications and conversions to laparotomy.
Conclusion: Total laparoscopic hysterectomy is a well-designed surgical procedure for the management of benign gynaecological conditions, and after adequate training, it seems to be a safe and effective procedure for patients.
Pedagogical Implication of Clause Expansion Mastery through E-Learning Instruction to Improve Academic English Writing Skills
Authors: I. Nurhamidah  , S. Purwanto  , C. Anwar  , D. F Wulandari  , A. Murtiningrum  
Published: August 2021

The current study investigated the pedagogical implication of Clause Expansion (CE) mastery to improve academic English writing skills. Fifteen students participated in the study. A two-cycle action research design was used to justify how the mastery of clause expansion contributed to the development of academic writing skills. Prior to intervention, they were assigned to write academic texts based on IELTS writing test. Then, they were given a three-week task-based e-learning instruction on CE., based on Systemic Functional Linguistic Framework of Clause Expansion.In the process of Explicit Instruction (EI) of CE, they were exposed in academic writing exercises to apply their knowledge on CE in various grammatical contexts in which it is required as Input Flood (IF). Another test was administered to see how it progressed from the pre-test. Then, another three-week task-based e-learning module, was given for their second online learning activities. A post-test was administered to see how it contributed to their overall writing skills. It turned out that CE mastery under e-learning special instruction did significantly improve their writing skills. They become more confident in writing academic texts. It is highly recommended that CE be taught as an integral part of a writing course.
Percepción de la violencia verbal entre estudiantes de educación secundaria obligatoria. Análisis y propuestas de mejora de la convivencia a través de la mediación.
Authors: Leiva Olivencia Juan , González Sodis José Luis , Matas Terrón Antonio 
Published: August 2021

Las investigaciones centradas en el diagnóstico de la convivencia dentro de nuestros entornos educativos son cada vez más relevantes a la hora de emprender medidas que mejoren al ambiente escolar de nuestros centros. Su importancia radica en conocer cuál es la percepción de la conflictividad para implementar programas conducentes a solventar los conflictos que surgen. Por ello, el objetivo del presente trabajo es analizar como perciben los estudiantes uno de los conflictos más comunes, la violencia verbal. La metodología de investigación es de carácter cuantitativo con un diseño no experimental realizado a partir de un cuestionario validado tipo Likert. Los análisis realizados son de tipo estadístico descriptivo e inferencial. La población está formada por 220 estudiantes de enseñanza secundaria obligatoria (ESO) de un centro concertado de Málaga (España). Los resultados, indican la existencia en el aula de un nivel significativo de violencia verbal entre el alumnado y en menor medida del alumnado hacia el profesorado, siempre desde la perspectiva de los estudiantes. Se concluye que la violencia verbal directa entre alumnos y docentes puede ser abordada con la implementación de la mediación escolar entre pares, herramienta que propone como fórmula adecuada para la gestión positiva de conflictos.
Prácticas digitales de estudiantes universitarios hondureños: estudio de caso
Authors: Cruz García Carlos Joselín , Zorrilla Abascal María Luisa 
Published: August 2021

Este trabajo presenta los resultados de un estudio de caso realizado en la Universidad Pedagógica Nacional Francisco Morazán (UPNFM) en Honduras. Dicho estudio tuvo como objetivo principal identificar y caracterizar las prácticas digitales de los estudiantes fuera y dentro del contexto escolar. Se trabajó desde la postura teórica y metodológica de los Estudios de Nuevos Medios y de los Estudios de Internet, ambas corrientes herederas de los Estudios de Medios (Media Studies). La investigación siguió las líneas metodológicas de la etnografía virtual. Se describen las diferentes técnicas e instrumentos para la recolección de los datos en las dos fases de la investigación: a) la aplicación de un cuestionario y b) la realización de entrevistas a profundidad, así como de e-observación. Se destaca la recuperación de c) un blog (diario digital) como medio para generar reflexiones por parte de los participantes. Los resultados abarcan diferentes aspectos de sus prácticas digitales: redes sociales que más frecuentan; recursos y aplicaciones para actividades de aprendizaje que más usan, hábitos lectores, así como ámbitos en que se manifiestan. Se considera de gran importancia el ahondar en estos temas, ya que no se han realizado investigaciones similares en Honduras y son pocos los estudios de este tipo ubicados en Centroamérica.
INFLUENCE OF TECHNOLOGY TYPE ON DEVELOPMENT OF INSTRUCTIONAL MATERIALS FOR DISTANCE EDUCATION
Authors: Njoki Hannah 
Published: August 2021

Purpose: no one technology can support all types of teaching and learning at a distance – the most effective approach is to combine a range of technologies. Using multiple technologies ensure that all learning styles are catered for and that significant opportunities for interaction between the learner and the tutor are provided. The general objective of the study was to evaluate influence of technology type on development of instructional materials for distance education.
Methodology: The paper used a desk study review methodology where relevant empirical literature was reviewed to identify main themes and to extract knowledge gaps.
Findings: From the study findings, it is concluded that learning through experience influences the creation of new values which become attitudes that have a strong impact on teacher's behavior towards e-learning technology. Therefore, the attitude and values are singled out as a separate category as well, linking together certain factors that influence them. Because of the manner of academic teaching process, the most commonly used is blended learning model where a course instructor chooses the e-learning technology based on certain elements. The practice has shown that creating a blended learning environment is not easy and that course instructors have problems in many stages of designing the virtual learning environment, from the analysis of the course requirements, analysis of the student requirements, application of instructional design model, e-learning technology use, not understanding the concept of the quality of e-learning process and many other factors..
Recommendations: The study recommends that is a need for more courses should be integrated in distance learning so as to cover all the courses offered to students. There is also need for students to enroll in practical classes for computer training. This will enable the less net savvy students to brace up so as to avoid being left behind by others. There is no doubt that a lot of pressures are facing our students when it comes to distance learning technology adoption, especially distance barrier. There is therefore, need for e-learning to be fully put in place to enable the group of students that their homes are far away from the school to participate in classes even when they are not able to make it to school. Finally, there should be availability of ICT infrastructure, the absence or inadequacy of which will totally hamper the idea of e-learning adoption in universities. There should be provision of computers and high bandwidth to enable the easy flow of classes online
El diseño en la economía mexicana, un acercamiento hacía su potencial como motor económico.
Authors: Moreno Leonardo , Rogel Villalba Erika 
Published: August 2021

Usualmente, el Diseño es reconocido como una práctica que actúa en la producción de bienes y experiencias para el consumo. Empero, ha sido poco significativo su valor como parte de la economía mexicana, aun cuando contribuye al aumento de la competitividad y valor añadido de productos y servicios. Algunos países, como Dinamarca, han entendido el potencial del Diseño como generador económico. Aunque en México, se han dado diversas iniciativas para mostrar su importancia estratégica en la competencia futura entre naciones, ciudades y empresas, la actividad del diseño en México, sigue sin ser considerada como algo urgente y el diseño se encuentra aún relegado del hacer productivo, social y económico del país. Este documento presenta un acercamiento a diversas áreas de oportunidad en que el Diseño contribuye a la economía y a la calidad de vida en las sociedades, área que aún demanda muchos estudios.
Study on fabrication of Sn-doped ZnO thin films oriented to the application for organic dye degradation catalysts in water environment
Authors: Vu Viet Doanh  , Nguyen Thu Trang  , Le Minh Kiet  , Duong Quoc Minh  , Trinh Quang Thong  , Le Hai Dang  
Published: August 2021

In this study, zinc oxide (ZnO) doped with Sn thin films were deposited on the glass substrate at 550 °C by dip-coating technique using the solution synthesized by sol-gel method. The structural, surface morphology, optical and photocatalytic property of thin films were studied. X-ray diffraction (XRD) analysis showed that the Sn-doping greatly changed the microstructure, morphology and optical properties of ZnO films, which may contribute to the enhancement of photocatalytic activity. Additionally, the photocatalytic activity was investigated using methylene blue dye under solar irradiation, with has high UV index from 7 to 8. The results indicated that Sn-doped ZnO had a higher photocatalytic activity and Sn dopant greatly increased the photocatalytic activity of ZnO thin film.
Modeling of land–surface interactions in the PALM model system 6.0: land surface model description, first evaluation, and sensitivity to model parameters
Authors: Gehrke Katrin Frieda , Sühring Matthias , Maronga Björn 
Published: August 2021

Abstract. In this paper the land surface model embedded in the PALM model system is described and evaluated against in situ measurements at Cabauw, Netherlands. A total of 2 consecutive clear-sky days are simulated, and the components of surface energy balance, potential temperature, humidity, and horizontal wind speed are compared to observations. For the simulated period, components of the energy balance are consistent with daytime and nighttime observations, and the daytime Bowen ratio also agrees fairly well with observations. The model simulates a more stably stratified nocturnal boundary layer than the observations, and near-surface potential temperature and humidity agree fairly well during the day. Moreover, a sensitivity analysis is performed to investigate dependence of the model on land surface and soil specifications, as well as atmospheric initial conditions, because they represent a major source of uncertainty in the simulation setup. It is found that an inaccurate estimation of leaf area index, albedo, or initial humidity causes a significant misrepresentation of the daytime turbulent sensible and latent heat fluxes. During the night, the boundary-layer characteristics are primarily affected by surface roughness and the applied radiation schemes.
An inventory of Alpine drought impact reports to explore past droughts in a mountain region
Authors: Stephan Ruth , Erfurt Mathilde , Terzi Stefano , Žun Maja , Kristan Boštjan , Haslinger Klaus , Stahl Kerstin 
Published: August 2021

Abstract. Drought affects the European Alpine mountain region, despite a humid climate. Droughts' damaging character in the past and increasing probability in future projections call for an understanding of drought impacts in the mountain regions. The European Drought Impact report Inventory (EDII) collects text reports on negative drought impacts. This study presents a considerably updated EDII focusing on the Alpine region. This first version release of an Alpine Drought Impact report Inventory (EDIIALPS) classifies impact reports into categories covering various affected sectors and enables comparisons of the drought impact characteristics. We analysed the distribution of reported impacts on the spatial, temporal and seasonal scale and by drought type for soil moisture drought and hydrological drought. For the spatial analysis, we compared the impact data located in the Alpine region to the whole of Europe. Furthermore, we compared impact data between different climatic and altitudinal domains (the northern region vs. the southern region and the pre-Alpine region vs. the high-altitude region) and between the Alpine countries. Compared to the whole of Europe, in the Alpine region agriculture and livestock farming impacts are even more frequently reported, especially in the southern region. Public water supply is the second most relevant sector but overall less prominent compared to Europe, especially in spring when snowmelt mitigates water shortages. Impacts occur mostly in summer and early autumn, with a delay between those impacts initiated by soil moisture and those initiated by hydrological drought. The high-altitude region shows this delay the strongest. From 1975 to 2020, the number of archived reports increases, with substantially more impacts noted during the drought events of 1976, 2003, 2015 and 2018. Moreover, reported impacts diversify from agricultural dominance to multi-faceted impact types covering forestry, water quality, industry and so forth. Though EDIIALPS is biased by reporting behaviour, the region-specific results of negative drought impacts across the water-rich European mountain region demonstrate the need to move from emergency response to prevention and preparedness actions. These may be guided by EDIIALPS' insights to regional patterns, seasons and drought types.