Duration and cost variability of construction activities: an empirical study

The unique nature of construction projects can mean that construction activities often suffer from duration and cost variability. Because this variability is unplanned, it can present a problem when attempting to complete a project on time and on budget. Various factors causing this variability have been identified in the literature, but they predominantly refer to the nature and/or context of the whole project rather than specific activities. In this paper, the order of magnitude of and correlation between activity duration and cost variability is analyzed in 101 construction projects with over 5,000 activities. To do this, the first four moments (mean, standard deviation, skewness, and kurtosis) of actual versus planned duration and cost (log) ratios are analyzed by project, phase of execution, and activity type. Results suggest that, contrary to common wisdom, construction activities do not end late on average. Instead, the large variability in the activity duration is the major factor causing significant project delays and cost overruns. The values of average activity duration and cost variability gathered in this study will also serve as a reference for construction managers to improve future construction planning and project simulation studies with more realistic data

Very Hard Electoral Control Problems

It is important to understand how the outcome of an election can be modified by an agent with control over the structure of the election. Electoral control has been studied for many election systems, but for all studied systems the winner problem is in P, and so control is in NP. There are election systems, such as Kemeny, that have many desirable properties, but whose winner problems are not in NP. Thus for such systems control is not in NP, and in fact we show that it is typically complete for $\Sigma_2^p$ (i.e., ${\rm NP}^{\rm NP}$, the second level of the polynomial hierarchy). This is a very high level of complexity. Approaches that perform quite well for solving NP problems do not necessarily work for $\Sigma_2^p$-complete problems. However, answer set programming is suited to express problems in $\Sigma_2^p$, and we present an encoding for Kemeny control.Comment: A version of this paper will appear in the Proceedings of AAAI-201

El gigante egoísta

REFLEXIONES CRÍTICAS Y TRADUCCIÓN DEL CUENTO DE OSCAR WILD

Impacto de la convivencia escolar sobre el rendimiento académico, desde la percepción de estudiantes con desarrollo típico y necesidades educativas especiales

This descriptive correlational study aims to compare the perception about eight dimensions of school coexistence of typically developing high school students (n = 545) and students with special educational needs (n = 75) from Chile and their relationship with the general academic performance.  Based on the analysis of hierarchical and non-hierarchical clusters, multiple regression and logistic regression, it was found that students with special educational needs have a less favorable perception in almost every dimension analyzed; especially, in those aspects related to school victimization, aggression, and indiscipline. Likewise, they perceive that they have a limited peer social network, as well as limited normative adjustment and a lower perception about their own positive interpersonal skills. The multiple regression and logistic regression models allow confirming that the dimensions of school coexistence account for between 20% and 27% of the academic performance variability. The aforementioned models highlight the role and negative effect of the level of victimization perceived by students, as well as the perception about the occurrence of indiscipline situations in the classroom, and the fact of belonging to the group of students with special educational needs, and to the group of male students. The findings are analyzed and discussed in light of the implications for high social vulnerability educational contexts.This descriptive correlational study aims to compare the perception about eight dimensions of school coexistence of typically developing high school students (n = 545) and students with special educational needs (n = 75) from Chile and their relationship with the general academic performance.  Based on the analysis of hierarchical and non-hierarchical clusters, multiple regression and logistic regression, it was found that students with special educational needs have a less favorable perception in almost every dimension analyzed; especially, in those aspects related to school victimization, aggression, and indiscipline. Likewise, they perceive that they have a limited peer social network, as well as limited normative adjustment and a lower perception about their own positive interpersonal skills. The multiple regression and logistic regression models allow confirming that the dimensions of school coexistence account for between 20% and 27% of the academic performance variability. The aforementioned models highlight the role and negative effect of the level of victimization perceived by students, as well as the perception about the occurrence of indiscipline situations in the classroom, and the fact of belonging to the group of students with special educational needs, and to the group of male students. The findings are analyzed and discussed in light of the implications for high social vulnerability educational contexts.Estudio descriptivo-correlacional que busca comparar la percepción acerca de ocho dimensiones de la convivencia escolar de estudiantes chilenos de educación media con desarrollo típico (n=545) y con necesidades educativas especiales (n=75), y su relación con el rendimiento académico general. A partir de los análisis de conglomerados jerárquico y no jerárquico, regresión múltiple y regresión logística, se constata que los estudiantes con necesidades educativas especiales tienen una percepción más desfavorable en casi todas las dimensiones analizadas, especialmente en aquellos aspectos asociados a la victimización escolar y agresión e indisciplina, de igual forma, perciben tener una menor red social de iguales, menor ajuste normativo y una más baja percepción respecto de la gestión interpersonal positiva. Los modelos de regresión múltiple y regresión logística, permiten constatar que las dimensiones de la convivencia escolar explican entre el 20% y el 27% de la variabilidad del rendimiento académico. En dichos modelos destaca el papel y efecto negativo que tiene la el grado de victimización que perciben los estudiantes, como también la percepción respecto de la ocurrencia o presencia de situaciones de indisciplina al interior del aula, como también el hecho de pertenecer al grupo de estudiantes con necesidades educativas especiales, y el pertenecer al grupo de estudiantes hombres. Se analizan y discuten los hallazgos a la luz de las implicaciones para contextos educativos de alta vulnerabilidad social

Adorno. Teoría crítica y dialéctica negativa

The work contains three sections. The wire of the text is the philosophical sustenance of the epistemologic structuring of Theodor W. Adorno. However, in the first part, the inheritance of some philosophers is exposed brief who left track in the structuring of the thought of the author. In the second section one appears, how one ties to him to Adornment with the Theory Criticizes; and finally, the posthumous work of the author is reviewed: Dialectic refusal.El trabajo contiene tres apartados. El hilo conductor del texto es el sustento filosófico de la estructuración epistemológica de Theodor W. Adorno. No obstante, en la primera parte, se expone breve la herencia de algunos filósofos que dejaron huella en la estructuración del pensamiento del autor. En el segundo apartado se presenta, cómo se le vincula a Adorno con la Teoría Critica; y por último, se reseña la obra póstuma del autor: Dialéctica negativa