Model and performance of a no-reference quality assessment metric for video streaming

Video streaming via Transmission Control Protocol (TCP) networks has become a popular and highly demanded service, but its quality assessment in both objective and subjective terms has not been properly addressed. In this paper, based on statistical analysis a full analytic model of a no-reference objective metric, namely pause intensity (PI), for video quality assessment is presented. The model characterizes the video playout buffer behavior in connection with the network performance (throughput) and the video playout rate. This allows for instant quality measurement and control without requiring a reference video. PI specifically addresses the need for assessing the quality issue in terms of the continuity in the playout of TCP streaming videos, which cannot be properly measured by other objective metrics such as peak signal-to-noise-ratio, structural similarity, and buffer underrun or pause frequency. The performance of the analytical model is rigidly verified by simulation results and subjective tests using a range of video clips. It is demonstrated that PI is closely correlated with viewers' opinion scores regardless of the vastly different composition of individual elements, such as pause duration and pause frequency which jointly constitute this new quality metric. It is also shown that the correlation performance of PI is consistent and content independent. © 2013 IEEE.

Anxiety sensitivity's facets in relation to anxious and depressive symptoms in youth

Anxiety sensitivity is a multifaceted cognitive risk factor currently being examined in relation to anxiety and depression. The paucity of research on the relative contribution of the facets of anxiety sensitivity to anxiety and depression, coupled with variations in existing findings, indicate that the relations remain inadequately understood. In the present study, the relations between the facets of anxiety sensitivity, anxiety, and depression were examined in 730 Hispanic-Latino and European-American youth referred to an anxiety specialty clinic. Youth completed the Childhood Anxiety Sensitivity Index, the Revised Children’s Manifest Anxiety Scale, and the Children’s Depression Inventory. The factor structure of the Childhood Anxiety Sensitivity Index was examined using ordered-categorical confirmatory factor analytic techniques. Goodness-of-fit criteria indicated that a two-factor model fit the data best. The identified facets of anxiety sensitivity included Physical/Mental Concerns and Social Concerns. Support was also found for cross-ethnic equivalence of the two-factor model across Hispanic-Latino and European-American youth. Structural equation modeling was used to examine models involving anxiety sensitivity, anxiety, and depression. Results indicated that an overall measure of anxiety sensitivity was positively associated with both anxiety and depression, while the facets of anxiety sensitivity showed differential relations to anxiety and depression symptoms. Both facets of anxiety sensitivity were related to overall anxiety and its symptom dimensions, with the exception being that Social Concerns was not related to physiological anxiety symptoms. Physical/Mental Concerns were strongly associated with overall depression and with all depression symptom dimensions. Social Concerns was not significantly associated with depression or its symptom dimensions. These findings highlight that anxiety sensitivity’s relations to youth psychiatric symptoms are complex. Results suggest that focusing on anxiety sensitivity’s facets is important to fully understand its role in psychopathology. Clinicians may want to target all facets of anxiety sensitivity when treating anxious youth. However, in the context of depression, it might be sufficient for clinicians to target Physical/Mental Incapacitation Concerns.

Oil Market Modelling: A Comparative Analysis of Fundamental and Latent Factor Approaches

We formally compare fundamental factor and latent factor approaches to oil price modelling. Fundamental modelling has a long history in seeking to understand oil price movements, while latent factor modelling has a more recent and limited history, but has gained popularity in other financial markets. The two approaches, though competing, have not formally been compared as to effectiveness. For a range of short- medium- and long-dated WTI oil futures we test a recently proposed five-factor fundamental model and a Principal Component Analysis latent factor model. Our findings demonstrate that there is no discernible difference between the two techniques in a dynamic setting. We conclude that this infers some advantages in adopting the latent factor approach due to the difficulty in determining a well specified fundamental model.

Modelling and Verification of a Correction Factor to Evaluate the Efficiency of Solar Thermal Collectors with the Rapid Test Method

A new method for the evaluation of the efficiency of parabolic trough collectors, called Rapid Test Method, is investigated at the Solar Institut Jülich. The basic concept is to carry out measurements under stagnation conditions. This allows a fast and inexpensive process due to the fact that no working fluid is required. With this approach, the temperature reached by the inner wall of the receiver is assumed to be the stagnation temperature and hence the average temperature inside the collector. This leads to a systematic error which can be rectified through the introduction of a correction factor. A model of the collector is simulated with COMSOL Multipyisics to study the size of the correction factor depending on collector geometry and working conditions. The resulting values are compared with experimental data obtained at a test rig at the Solar Institut Jülich. These results do not match with the simulated ones. Consequentially, it was not pos-sible to verify the model. The reliability of both the model with COMSOL Multiphysics and of the measurements are analysed. The influence of the correction factor on the rapid test method is also studied, as well as the possibility of neglecting it by measuring the receiver’s inner wall temperature where it receives the least amount of solar rays. The last two chapters analyse the specific heat capacity as a function of pressure and tem-perature and present some considerations about the uncertainties on the efficiency curve obtained with the Rapid Test Method.

Spectral self-action of THz emission from ionizing two-color laser pulses in gases

The spectrum of terahertz (THz) emission in gases via ionizing two-color femtosecond pulses is analyzed by means of a semi-analytic model and numerical simulations in 1D, 2D and 3D geometries taking into account propagation effects of both pump and THz fields. We show that produced THz signals interact with free electron trajectories and thus significantly influence further THz generation upon propagation, i.e., make the process inherently nonlocal. This self-action contributes to the observed strong spectral broadening of the generated THz field. Weshow that diffraction of the generated THz radiation is the limiting factor for the co-propagating low frequency amplitudes and thus for the self-action mechanism in 2D and 3D geometries.

Spectral self-action of THz emission from ionizing two-color laser pulses in gases

The spectrum of terahertz (THz) emission in gases via ionizing two-color femtosecond pulses is analyzed by means of a semi-analytic model and numerical simulations in 1D, 2D and 3D geometries taking into account propagation effects of both pump and THz fields. We show that produced THz signals interact with free electron trajectories and thus significantly influence further THz generation upon propagation, i.e., make the process inherently nonlocal. This self-action contributes to the observed strong spectral broadening of the generated THz field. We show that diffraction of the generated THz radiation is the limiting factor for the co-propagating low frequency amplitudes and thus for the self-action mechanism in 2D and 3D geometries.

Impacto de la resiliencia en pacientes con Artritis Reumatoide

Introducción: La artritis reumatoide (AR) es una enfermedad autoinmune-inflamatoria, que compromete las articulaciones diartrodiales. Tiene una importante repercusión sistémica que incluye la depresión; por lo tanto, tiene un severo impacto sobre la calidad de vida. Es posible que mecanismos de defensa, tales como la resiliencia, puedan amortiguar dicho impacto. Metodología: estudio de corte transversal, multicéntrico (análisis inicial dentro del grupo AR, con muestra no probabilística de 66 pacientes, posterior selección aleatoria simple de 16 pacientes de la muestra inicial y selección de 16 individuos sanos pareados). Posteriormente, se comparó la resiliencia entre sujetos con AR y sujetos sanos, mediante las escalas RS y CD-RISC25. Adicionalmente, se aplicaron las escalas EEAE, EADZ, SF-36 y PANAS. Los datos fueron evaluados mediante el coeficiente de correlación de Spearman, las pruebas U Mann-Whitney, Kruskall-Wallis, T de Student y análisis de varianza. Resultados: se encontraron diferencias significativas en las estrategias de afrontamiento no espirituales en grupos de resiliencia baja, media y alta; diferencias en las medianas de resiliencia en los grupos de depresión por EAZD en los pacientes. No se encontraron resultados significativos en las variables clínicas de la AR ni en la comparación con sujetos sanos. Conclusiones: el uso de estrategias de afrontamiento no espirituales y la ausencia de depresión, se asoció a mayores niveles de resiliencia en los pacientes con AR, por lo cual, los componentes emocionales y cognitivos se asocian a la resiliencia.

Congruencia entre los valores personales y organizacionales y su influencia con el engagement en el trabajo : estudio de caso en una organización del sector salud

La capacidad de gestión del personal se ha convertido en un imperativo para las organizaciones modernas. Por tanto se vienen introduciendo temas como la administración en valores y el engagement de los trabajadores. Sin embargo, la relación entre estos dos aún no ha sido estudiada. El presente estudio tiene como objetivo analizar el efecto que tiene el grado de articulación y reconocimiento de los valores organizacionales y personales y organizacionales sobre los niveles de engagement de los empleados. Para esta investigación se utilizó una muestra constituida por 54 trabajadores de una organización del sector salud de la ciudad de Bogotá a quienes les fueron aplicadas dos escalas: el Inventario para Medir la Articulación entre la Persona y la Organización (Inventario APO) y Utrech Work Engagement Scale (UWES). Como principal resultado se obtuvo que de las tres dimensiones consideradas predictoras del engagement, solamente el reconocimiento de los valores organizacionales tuvo un efecto estadísticamente significativo.

Fatores gravimétricos no Brasil para um modelo anelástico de Terra

Geodetic observations are affected by the disturbing potential of the luni-solar tide. Among those observations, the value of g obtained from gravimetric survey needs correction by the gravimetric factor. This correction is derived from the Numbers of Love, which depend on the adopted model of Earth. Because of this, it is necessary to update the correction since the gravimetric factor widely used in Brazil as delta = 1.20 does not consider local rheological variations and they are latitude dependent. A discrepancy of about 1% between the observed tidal gravimetric factors d of the ""Trans World Tidal Gravity Profiles"" (TWTGP), related to Brussels fundamental station, and those obtained by recent observations reported by Freitas and Ducarme ( 1991). Experiments based on inertial force effects also reveal a variation of about 0.5% in the observed d. A same order of magnitude difference is obtained for an anelastic Earth model when compared with a viscous-elastic model and even when different frequencies of tidal perturbations are considered. In this paper regression models are presented for gravimetric factors for the lunar components O(1) and M(2) in Brazil. These models were obtained from observations performed at stations belonging to the Brazilian segment of the TWTGP.

Piezoresistive response of ITO films deposited at room temperature by magnetron sputtering

Indium tin oxide (ITO) thin films have been deposited on (100) Si substrates by RF magnetron sputtering from a compact target (90% In(2)O(3)-10% SnO(2) in weight) with 6 in. in diameter. In order to perform electromechanical characterizations of these films, strain gauges were fabricated. An experimental set-up based on bending beam theory was developed to determine the longitudinal piezoresistive coefficient (pi(1)) of the strain gauges fabricated. It has been confirmed that electrical resistance of the strain gauges decreases with load increases which results a negative gauge factor. A model based on the activation energy was used to explain the origin of this negative signal. The influence of the temperature on piezoresistive properties of ITO films was also evaluated.

Using a combination of MLPA kits to detect chromosomal imbalances in patients with multiple congenital anomalies and mental retardation is a valuable choice for developing countries

Conventional karyotyping detects anomalies in 3-15% of patients with multiple congenital anomalies and mental retardation (MCA/MR). Whole-genome array screening (WGAS) has been consistently suggested as the first choice diagnostic test for this group of patients, but it is very costly for large-scale use in developing countries. We evaluated the use of a combination of Multiplex Ligation-dependent Probe Amplification (MLPA) kits to increase the detection rate of chromosomal abnormalities in MCA/MR patients. We screened 261 MCA/MR patients with two subtelomeric and one microdeletion kits. This would theoretically detect up to 70% of all submicroscopic abnormalities. Additionally we scored the de Vries score for 209 patients in an effort to find a suitable cut-off for MLPA screening. Our results reveal that chromosomal abnormalities were present in 87 (33.3%) patients, but only 57 (21.8%) were considered causative. Karyotyping detected 15 abnormalities (6.9%), while MLPA identified 54 (20.7%). Our combined MLPA screening raised the total detection number of pathogenic imbalances more than three times when compared to conventional karyotyping. We also show that using the de Vries score as a cutoff for this screening would only be suitable under financial restrictions. A decision analytic model was constructed with three possible strategies: karyotype, karyotype + MLPA and karyotype + WGAS. Karyotype + MLPA strategy detected anomalies in 19.8% of cases which account for 76.45% of the expected yield for karyotype + WGAS. Incremental Cost Effectiveness Ratio (ICER) of MLPA is three times lower than that of WGAS, which means that, for the same costs, we have three additional diagnoses with MLPA but only one with WGAS. We list all causative alterations found, including rare findings, such as reciprocal duplications of regions deleted in Sotos and Williams-Beuren syndromes. We also describe imbalances that were considered polymorphisms or rare variants, such as the new SNP that confounded the analysis of the 22q13.3 deletion syndrome. (C) 2011 Elsevier Masson SAS. All rights reserved.

How cracks in SiOx-coated polyester films affect gas permeation

In this paper theoretical models have been established that can account for the gas transmission through nanocomposite laminates, consisting of an oxide layer of finite permeability containing defects, on a polymer sheet of finite thickness. The defect shapes can either be in the form of long cracks or rectangular holes. The models offer a choice of exact numerical calculations or fast and intuitive analytical approximations. The experimental measurements of oxygen permeation through four different SiOx/poly (ethylene terephthalate) samples that were strained to produce distributions or cracks showed good agreement when compared with predicted results from the approximate analytic model. As a consequence of this observation, a key practical conclusion is that, because of the logarithmic dependence of transmission on the width of a crack, for a given strain it is better to have a small number of large cracks rather than a large number of small cracks. (C) 2001 Elsevier Science B.V. All rights reserved.

The impact of family control on firm's return

Family firm is a field of growing interest. The aim of this article is to understand whether CEOs identity impacts family firm’s stock returns. From a sample of Portuguese and Spanish family firms findings show that who manages the firms result in significantly different risk exposure. Moreover, we find that the abnormal return found by Fahlenbrach (2009) to founder-controlled firms disappear when we use valueweighted portfolios and include two new factors: market aggregate illiquidity and debt intensity to the four-factor Carhart model. Finally, our results explain why the majority of family firm is controlled by its founder.

Factorial validity of the Maslach Burnout Inventory (MBI-HSS) among Spanish professionals

OBJECTIVE: To assess the factorial validity and internal consistency of the Maslach Burnout Inventory (MBI-HSS). METHODS: In a sample consisting of 705 Spanish professionals from diverse occupational sectors (health, education, police and so one), seven plausible factorial models hypothesized were compared using LISREL 8. RESULTS: The four-factor oblique solution and the three-factor oblique solution showed the best and similar fit. Deletion of Item 12 and Item 16, taking into consideration the suggestions in the manual, improved the goodness of fit for both models. The four-factor oblique model suggests that, in addition to Emotional Exhaustion (EE) and Depersonalization (DP), Personal Accomplishment (PA) consists of two components labeled here Self-Competence (Items 4, 7, 17, and 21) and the Existential Component (Items 9, 12, 18, and 19). However, the alpha coefficient was relatively low for the Self-Competence component, suggesting that it is more suitable to estimate the syndrome as a threedimensional construct. The Cronbach's alpha was satisfactory for PA (alpha =.71) and EE (alpha =.85), and moderate for DP (alpha =.58). CONCLUSIONS: The results show that the MBI-HSS offers factorial validity and its scales present internal consistency to evaluate the quality of working life for Spanish professionals.

Estudo empírico da caracterização da selecção de fornecedores

O problema de selecção de fornecedores/parceiros é uma parte integrante e importante nas empresas que se propõem a um desempenho competitivo e lucrativo na sua área de actividade. A escolha do melhor fornecedor/parceiro passa na maior parte da vezes por fazer uma análise cuidada dos factores que podem influenciar positiva ou negativamente essa escolha. Desde cedo este problema tem vindo a ser alvo de inúmeros estudos, estudos esses que se focam essencialmente nos critérios a considerar e nas metodologias a adoptar para optimizar a escolha dos parceiros. De entre os vários estudos efectuados, muitos são os que consideram como critérios chave o custo do produto, a qualidade, a entrega e a reputação da empresa fornecedora. Ainda assim, há muitos outros que são referidos e que na sua maioria se apresentam como subcritérios. No âmbito deste trabalho, foram identificados cinco grandes critérios, Qualidade, Sistema Financeiro, Sinergias, Custo e Sistema Produtivo. Dentro desses critérios, sentiu-se a necessidade de incluir alguns subcritérios pelo que, cada um dos critérios chave apresenta cinco subcritérios. Identificados os critérios, foi necessário perceber de que forma são aplicados e que modelos são utilizados para se poder tirar o melhor partido das informações. Sabendo que existem modelos que privilegiam a programação matemática e outros que fazem uso de ponderações lineares para se identificar o melhor fornecedor, foi realizado um inquérito e contactadas empresas por forma a perceber quais os factores que mais peso tinham nas suas decisões de escolha de parceiros. Interpretados os resultados e tratados os dados foi adoptado um modelo de ponderação linear para traduzir a importância de cada um dos factores. O modelo proposto apresenta uma estrutura hierárquica e pode ser aplicado com o método AHP de Saaty ou o método de Análise de Valor. Este modelo permite escolher a ou as alternativas que melhor se adequam aos requisitos das empresas.