Investigation on average void fraction for air/non-Newtonian power-law fluids two-phase flow in downward inclined pipes

The present work has been carried out to investigate on the average void fraction of gas/non-Newtonian fluids flow in downward inclined pipes. The influences of pipe inclination angle on the average void fraction were studied experimentally. A simple correlation, which incorporated the method of Vlachos et al. for gas/Newtonain fluid horizontal flow, the correction factor of Farooqi and Richardson and the pipe inclination angle, was proposed to predict the average void fraction of gas/non-Newtonian power-law stratified flow in downward inclined pipes. The correlation was based on 470 data points covering a wide range of flow rates for different systems at diverse angles. A good agreement was obtained between theory and data and the fitting results could describe the majority of the experimental data within ±20%.

Verification of a scaling law in few-cycle laser pulses

The scaling law of photoionization in few-cycle laser pulses is verified in this paper. By means of numerical solution of time-dependent Schrodinger equation, the photoionization and the asymmetry degree of photoionization of atoms with different binding potential irradiated by various laser pulses are studied. We find that the effect of increasing pulse intensity is compensated by deepening the atomic binding potential. In order to keep the asymmetric photoionization unchanged, if the central frequency of the pulse is enlarged by k times, the atomic binding potential should also be enlarged by k times, and the laser intensity should be enlarged by k(3) times. (c) 2005 Optical Society of America.

A scaling law of photoionization in ultrashort pulses

By means of the numerical solution of time-dependant Schrodinger equation, we verify a scaling law of photoionization in ultrashort pulses. We find that for a given carrier-envelope phase and duration of the pulse, identical photoionizations are obtained provided that when the central frequency of the pulse is enlarged by k times, the atomic binding potential is enlarged by k times, and the laser intensity is enlarged by k(3) times. The scaling law allows us to reach a significant control over direction of photoemission and offers exciting prospects of reaching similar physical processes in different interacting systems which constitutes a novel kind of coherent control.

A scaling law of photoelectron angular distributions in one-cycle laser pulses

The photoelectron angular distributions (PADs) from above-threshold ionization of atoms irradiated by one-cycle laser pulses satisfy a scaling law. The scaling law denotes that the main features of the PADs are determined by four dimensionless parameters: (1) the ponderomotive number u(p) = U-p/hw, the ponderomotive energy U-p in units of laser photon energy; (2) the binding number E-b = E-b/h(w), the atomic binding energy E-b in units of laser photon energy; (3) the number of absorbed photons q; (4) the carrier-envelope phase phi(0), the phase of the carrier wave with respect to the envelope. We verify the scaling law by theoretical analysis and numerical calculation, compared to that in long-pulse case. A possible experimental test to verify the scaling law is suggested.

Modified formula of Malus' law for Glan-Taylor polarizing prisms

A simple three-axis model has been developed, which has been successfully applied to the analysis of the light transmittance in spatial incident angle and the simulation of modified formula of Malus' law for Glan-Taylor prisms. Our results indicate that the fluctuations on the cosine squared curve are due to specific misalignments between the axis of the optical system, the optical axis of the prism and the mechanical axis (rotation axis) of prism, which results in the fact that different initial relative location of the to-be-measured-prism in the testing system corresponds to different shape of Malus' law curve. Methods to get absolutely smooth curve are proposed. This analysis is available for other kinds of Glan-type prisms. (C) 2004 Elsevier B.V. All rights reserved.

A scaling law of photoionization in few-cycle regime

In this paper, a scaling law of photoionization of atoms irradiated by intense, few- cycle laser pulses is established. The scaling law sets a relation to the phase- dependent ionization with the kinetic energy of photoelectrons, the duration and peak intensity of short pulses, and the ionization potential of the target atoms. We find that it will be advantageous to manifest the phase- dependent photoionization by choosing the target atoms with larger ionization potential, using laser with smaller carrier- frequency, and increasing the pulse intensity. (c) 2007 Optical Society of America.

Addressing students' difficulties with Faraday's law: A guided problem solving approach

In traditional teaching, the fundamental concepts of electromagnetic induction are usually quickly analyzed, spending most of the time solving problems in a more or less rote manner. However, physics education research has shown that the fundamental concepts of the electromagnetic induction theory are barely understood by students. This article proposes an interactive teaching sequence introducing the topic of electromagnetic induction. The sequence has been designed based on contributions from physics education research. Particular attention is paid to the relationship between experimental findings (macroscopic level) and theoretical interpretation (microscopic level). An example of the activities that have been designed will also be presented, describing the implementation context and the corresponding findings. Since implementing the sequence, a considerable number of students have a more satisfactory grasp of the electromagnetic induction explicative model. However, difficulties are manifested in aspects that require a multilevel explanation, referring to deep structures where the system description is better defined.

Luzes e sombras na construção de um caminho para pacientes incuráveis: a eutanásia à luz da bioética e do direito

A presente dissertação analisa a possibilidade da prática da eutanásia ativa e voluntária em pacientes com doenças incuráveis à luz da bioética e do direito. O trabalho é de natureza teórica e foi realizado através de pesquisa bibliográfica, que levantou publicações, nacionais e internacionais, inclusive na imprensa, sobre os temas tratados na dissertação, a saber: eutanásia, morte, vida, dignidade, autonomia, princípios bioéticos, liberdade. O levantamento bibliográfico compreendeu, preferencialmente, obras sobre filosofia, ética, bioética, medicina e direito, que permitiram a análise das questões teóricas envolvidas diretamente no estudo. Aborda-se o conceito de morte e suas transformações ao longo dos anos e as distinções necessárias entre os conceitos do fim da vida, que apesar de muito próximos tem suas especificidades. Apresenta-se os princípios bioéticos da não maleficência e da beneficência, com a finalidade de discutir os limites da intervenção médica sobre o paciente, bem como o princípio da autonomia na visão da bioética e do direito, com o intuito de demonstrar que o doente incurável é um ser autônomo, com vontades e desejos que devem ser respeitados. Examinam-se os direitos à vida e a liberdade para fins de ponderação em face do princípio da dignidade da pessoa humana. Diferenciam-se os princípios da sacralidade da vida e da qualidade da vida, na busca de uma integração entre eles e faz-se uma análise do Código de Ética Médica e da Resolução CFM n 1.805 de 2006, que autoriza a ortotanásia, para confrontar os limites da prática médica e da autonomia do paciente. Pontua-se o estado atual da criminalização da eutanásia no ordenamento jurídico brasileiro apontando-se o quão perversa pode se tornar essa criminalização para aquele que sofre e, que através da compaixão laica e da solidariedade deve-se buscar meios hábeis para se permitir a eutanásia, sem deixar de proteger os vulnerados de eventuais abusos. Utilizam-se os casos de Ramón Sampedro e Vincent Humbert, pessoas que por causa de um acidente ficaram tetraplégicas e solicitaram na justiça uma morte digna, para exemplificar os diversos conceitos utilizados nesse trabalho. Por fim, apresentam-se os requisitos pessoais e formais mínimos para que a declaração de vontade de um paciente incurável, que pede uma morte digna, seja respeitada, quando essa vontade é expressa de forma inequívoca por ele, tendo como exemplo, a legislação da Bélgica e da Holanda, onde a eutanásia é permitida observando-se determinados requisitos.