A Lindley-type equation arising from a carousel problem

Abstract: In this paper we consider a system with two carousels operated by one picker. The items to be picked are randomly located on the carousels and the pick times follow a phasetype distribution. The picker alternates between the two carousels, picking one item at a time. Important performance characteristics are the waiting time of the picker and the throughput of the two carousels. The waiting time of the picker satisfies an equation very similar to Lindley’s equation for the waiting time in the P H/U/1 queue. Although the latter equation has no simple solution, it appears that the one for the waiting time of the picker can be solved explicitly. Furthermore, it is well known that the mean waiting time in the P H/U/1 queue depends on to the complete inter-arrival time distribution, but numerical results show that, for the carousel system, the mean waiting time and throughput are rather insensitive to the pick-time distribution

Tipología circadiana y problemas de salud mental

La tipología circadiana (matutina, vespertina o intermedia) es una diferencia individual que se ha relacionado con numerosos aspectos de la salud mental. En este estudio se revisan los principales hallazgos publicados en el área. Tras la búsqueda bibliográfica en las principales bases de datos se seleccionaron un total de 70 artículos publicados en castellano e inglés entre los años 1990 y 2012, recogidos en las bases de datos ISI, Scopus y Medline, donde se muestra que los individuos vespertinos presentan una mayor prevalencia de trastorno afectivo estacional, depresión mayor, trastorno bipolar, esquizofrenia, trastornos de la conducta alimentaria, trastornos del sueño, conductas adictivas, TDAH y mayores niveles de ansiedad que los matutinos. La tipología vespertina se perfila como un factor de riesgo y la matutina como un factor protector para el desarrollo de diversas psicopatologías, apuntándose como posibles causas polimorfismos de los genes reloj, el jet-lag social y algunos rasgos de personalidad. La tipología circadiana debe considerarse en la evaluación, tratamiento y prevención de las psicopatologías, pues afecta al inicio, curso, remisión y recaída de las mismas. La utilización de terapia cronobiológica es un factor a tener en cuenta en el abordaje terapéutico cuando la expresión rítmica circadiana se halla alterada

Zero-th law in structural glasses: an example

We investigate the validity of a zeroth thermodynamic law for non-equilibrium systems. In order to describe the thermodynamics of the glassy systems, it has been introduced an extra parameter, the effective temperature which generalizes the fluctuation-dissipation theorem (FDT) to off-equilibrium systems and supposedly describes thermal fluctuations around the aging state. In particular we analyze two coupled systems of harmonic oscillators with Monte Carlo dynamics. We study in detail two types of dynamics: sequential dynamics, where the coupling between the subsystems comes only from the Hamiltonian; and parallel dynamics where there is another source of coupling: the dynamics. We show how in the first case the effective temperatures of the two interacting subsystems are different asymptotically due to the smallness of the thermal conductivity in the aging regime. This explains why, in structural glasses, different interacting degrees of freedom can stay at different effective temperatures, and never thermalize.Comment: 10 pages. Contribution to the Proceedings of the ESF SPHINX meeting `Glassy behaviour of kinetically constrained models' (Barcelona, March 22-25, 2001). To appear in a special issue of J. Phys. Cond. Mat

A research review on healthy lifestyle of university students through statistical approach

This paper shows different methods to analyse the survey questions that related to healthy lifestyle or the factors affect it. The factors included eating habits, health factors, exercise and entertainment. The steps normally start with survey method which there are many types of method to undergo data collection and then undergo the pilot study. In descriptive summary, it is needed to obtain the essential part of information in the whole study first before undergo analysis. Data analysis included some statistical tests are done to know the association within variables. There are also some methods that were used to measure the satisfaction level of the consumers in the organisations

Assessment of livestock marketing associations in arid and semi-arid lands in northern Kenya

United States Agency for International Developmen

ANALYSIS OF THE EFFECT OF SOIL CHARACTERISTICS ON THE DRAINAGE OF DRAINAGE ON SOIL RETAINING WALLS

There are a number of cases of crushing land holders when they occur and afterwards it rains, this collapse is expected to occur due to rainwater that weighed on excessively. Rainwater makes the land around can contain plenty of water so that weighs over the walls of the land excessively and does not inade the drainage system to drain the water so that the wall of the ground is collapsed. The purpose of this study is to find out how influence the characteristics of clay and sand land on distilled drainage on the walls of the landbreak. This research was conducted in the lab with a land characteristic test then made the wall prototype of ground retaining, distilled simulation testing and analysis of clay and sand stability wall stability, with different groundwater faces according to the height of the drainage pipe, the analysis was carried out manually. From the test results of clay and sand in the lab found value c, ø , γ, wc, Gs,k. on clay land obtained permeability values , While the value of sand permeability . Of the two values ​​sand faster in flowing water. After testing the rain simulation of clamp soil levels increased by 18.24% while sand increased by 8.62%, this proved that more water settled in clay. The results of the analysis of the stability of the ground retaining wall with the noise can reduce the horizontal load caused by water.   &nbsp

Bases cerebrales de la atención sostenida y la memoria de trabajo: un estudio de resonancia magnética funcional basado en el Continuous Performance Test

Introducción. Uno de los paradigmas más utilizados en el estudio de la atención es el Continuous Performance Test (CPT). La versión de pares idénticos (CPT-IP) se ha utilizado ampliamente para evaluar los déficits de atención en los trastornos del neurodesarrollo, neurológicos y psiquiátricos. Sin embargo, la localización de la activación cerebral de las redes atencionales varía significativamente según el diseño de resonancia magnética funcional (RMf) usado. Objetivo. Diseñar una tarea para evaluar la atención sostenida y la memoria de trabajo mediante RMf para proporcionar datos de investigación relacionados con la localización y el papel de estas funciones. Sujetos y métodos. El estudio contó con la participación de 40 estudiantes, todos ellos diestros (50%, mujeres; rango: 18-25 años). La tarea de CPT-IP se diseñó como una tarea de bloques, en la que se combinaban los períodos CPT-IP con los de reposo. Resultados. La tarea de CPT-IP utilizada activa una red formada por regiones frontales, parietales y occipitales, y éstas se relacionan con funciones ejecutivas y atencionales. Conclusiones. La tarea de CPT-IP utilizada en nuestro trabajo proporciona datos normativos en adultos sanos para el estudio del sustrato neural de la atención sostenida y la memoria de trabajo. Estos datos podrían ser útiles para evaluar trastornos que cursan con déficits en memoria de trabajo y en atención sostenida.Introduction. One of the most used paradigms in the study of attention is the Continuous Performance Test (CPT). The identical pairs version (CPT-IP) has been widely used to evaluate attention deficits in developmental, neurological and psychiatric disorders. However, the specific locations and the relative distribution of brain activation in networks identified with functional imaging, varies significantly with differences in task design. Aim. To design a task to evaluate sustained attention using functional magnetic resonance imaging (fMRI), and thus to provide data for research concerned with the role of these functions. Subjects and methods. Forty right-handed, healthy students (50% women; age range: 18-25 years) were recruited. A CPT-IP implemented as a block design was used to assess sustained attention during the fMRI session. Results. The behavioural results from the CPT-IP task showed a good performance in all subjects, higher than 80% of hits. fMRI results showed that the used CPT-IP task activates a network of frontal, parietal and occipital areas, and that these are related to executive and attentional functions. Conclusions. In relation to the use of the CPT to study of attention and working memory, this task provides normative data in healthy adults, and it could be useful to evaluate disorders which have attentional and working memory deficits