Modelamento netrosférico aumentado para a determinação de campos de vapor d’água atmosféricos com base em sinais de alta resolução gnss

Signals of global navigation satellite systems (GNSS) are delayed by propagatingthrough the Earth’s electrically neutral atmosphere. This delay term plays animportant role in GNSS positioning and has been taken into account in highprecisiongeodetic applications. The neutrospheric delay can be subdivided into adry and a complementary wet component. The wet component amounts to typicallyless than 10% of the total neutrospheric delay and can be used to determine highresolutionatmospheric water vapour fields based on extended neutrosphericmodelling. The approach outlined in the present paper combines empiricalneutrospheric a priori model, site-specific neutrosphere parameters and residuals ofGNSS phase observations. Using so-called single-layer models, the derivedatmospheric water vapour fields are two-dimensionally reconstructed andvisualised. Applying this extended neutrospheric model to generate water vapourfields within a regional GNSS network, the results indicate that both the temporaland the spatial resolution of the determined water vapour fields are improved incomparison to the conventional neutrospheric modelling.Os sinais oriundos dos sistemas de navegação globais por satélite (GNSS) sofremum atraso durante sua propagação através da camada eletricamente neutra daatmosfera terrestre. Este atraso tem um papel fundamental no posicionamentoGNSS e tem sido levado em conta nas aplicações geodésicas de alta precisão. Oatraso neutrosférico pode ser subdividido em uma componente seca e umacomponente complementar úmida. A quantidade correspondente a componenteúmida é tipicamente inferior a 10% do atraso total, e pode ser utilizada nadeterminação de campos de vapor d’água atmosférico de alta resolução baseados nomodelo aumentado da neutrosfera. A abordagem apresentada neste trabalhocombina um modelo a priori empirico, parâmetros neutrosféricos específicos daestação e resíduos das observações de fase GNSS. Utilizando os chamados modelosde camada única, os campos de vapor d’água atmosférico derivados sãoreconstruídos e visualizados, ambos em duas dimensões. Utilizando este modeloneutrosférico aumentado na geração de campos de vapor d’água dentro de uma rederegional GNSS, os resultados indicam uma melhora tanto na resolução temporalquanto na espacial dos campos de vapor d’água determinados, quando comparadoscom a modelagem neutrosférica convencional

IMPACT OF VARIOUS FACTORS ON THE QUALITY OF SITE-SPECIFIC NEUTROSPHERIC PARAMETERS WITHIN GNSS DATA PROCESSING: A CASE STUDY

Os atrasos na propagação dos sinais dos sistemas de navegação globais por satélite (GNSS), causados pela atmosfera neutra, são importantes fatores que limitam a acurácia de aplicações geodésicas precisas. Uma abordagem comum para tratar o atraso neutrosférico é estimar os chamados parâmetros neutrosféricos específicos da estação (SSNP – site-specific neutrospheric parameters) no processamento de dados GNSS, os quais são, então, combinados com valores de um modelo predito calculados principalmente utilizando dados meteorológicos. Portanto, a qualidade do atraso neutrosférico determinado depende não somente dos efeitos que atuam nos sinais GNSS, mas também da estratégia utilizada no processamento dos dados. Neste trabalho, as influências dos fatores que afetam a modelagem neutrosférica como: o comprimento da linha de base, multicaminho, ponderação do peso das observações, resolução das ambigüidades e o modelo de predição neutrosférica, são analisados e quantificados baseando-se nos desvios-padrão dos SSNP estimados. Além disso, um modelo melhorado para a ponderação dos pesos das observações, baseado nas medidas de potência da razão sinal-ruído, é brevemente descrito. Os resultados apresentados nos testes indicam que a aplicação deste avançado modelo de ponderação dos pesos no processamento de dados GNSS, incluindo observações com baixa elevação, pode melhorar os desvios-padrão dos SSNP estimados em torno de 25% comparado com o modelo padrão de ponderação dos pesos dependente de elevação.Propagation delays of the signals of global navigation satellite systems (GNSS) caused by the neutral atmosphere are an important accuracy-limiting factor for precise geodetic applications. A common approach to handle the neutrospheric delay is to estimate so-called site-specific neutrospheric parameters (SSNP) within GNSS data processing which are then combined with the predicted model values calculated primarily based on meteorological data. Therefore, the quality of the determined neutrospheric delay depends not only on the factors impacting the GNSS signals but also on data processing strategies. In this paper, the influence of the factors impacting neutrospheric modelling such as baseline length, multipath, observation weighting, ambiguity resolution, and neutrospheric prediction models are analysed and quantified based on the standard deviations of the estimated SSNP. Additionally, an improved observation weighting scheme based on signal-to-noise power ratio measurements is briefly described. Test results indicate that applying this advanced weight model within GNSS data processing, including observations at low elevation, the standard deviation of the estimated SSNP can be improved by nearly 25% compared with the standard elevation-dependent weighting model

Vacancy-assisted domain-growth in asymmetric binary alloys: a Monte Carlo study

A Monte Carlo simulation study of the vacancy-assisted domain-growth in asymmetric binary alloys is presented. The system is modeled using a three-state ABV Hamiltonian which includes an asymmetry term, not considered in previous works. Our simulated system is a stoichiometric two-dimensional binary alloy with a single vacancy which evolves according to the vacancy-atom exchange mechanism. We obtain that, compared to the symmetric case, the ordering process slows down dramatically. Concerning the asymptotic behavior it is algebraic and characterized by the Allen-Cahn growth exponent x=1/2. The late stages of the evolution are preceded by a transient regime strongly affected by both the temperature and the degree of asymmetry of the alloy. The results are discussed and compared to those obtained for the symmetric case.Comment: 21 pages, 9 figures, accepted for publication in Phys. Rev.

Anomalous Dynamics of Forced Translocation

We consider the passage of long polymers of length N through a hole in a membrane. If the process is slow, it is in principle possible to focus on the dynamics of the number of monomers s on one side of the membrane, assuming that the two segments are in equilibrium. The dynamics of s(t) in such a limit would be diffusive, with a mean translocation time scaling as N^2 in the absence of a force, and proportional to N when a force is applied. We demonstrate that the assumption of equilibrium must break down for sufficiently long polymers (more easily when forced), and provide lower bounds for the translocation time by comparison to unimpeded motion of the polymer. These lower bounds exceed the time scales calculated on the basis of equilibrium, and point to anomalous (sub-diffusive) character of translocation dynamics. This is explicitly verified by numerical simulations of the unforced translocation of a self-avoiding polymer. Forced translocation times are shown to strongly depend on the method by which the force is applied. In particular, pulling the polymer by the end leads to much longer times than when a chemical potential difference is applied across the membrane. The bounds in these cases grow as N^2 and N^{1+\nu}, respectively, where \nu is the exponent that relates the scaling of the radius of gyration to N. Our simulations demonstrate that the actual translocation times scale in the same manner as the bounds, although influenced by strong finite size effects which persist even for the longest polymers that we considered (N=512).Comment: 13 pages, RevTeX4, 16 eps figure

Extension of the sum rule for the transition rates between multiplets to the multiphoton case

The sum rule for the transition rates between the components of two multiplets, known for the one-photon transitions, is extended to the multiphoton transitions in hydrogen and hydrogen-like ions. As an example the transitions 3p-2p, 4p-3p and 4d-3d are considered. The numerical results are compared with previous calculations.Comment: 10 pages, 4 table

Antecedents and outcomes of consumer environmentally friendly attitudes and behaviour

With the intensification of problems relating to the environment, a growing number of consumers are becoming more ecologically conscious in their preferences and purchases of goods. This paper presents the results of a study conducted among 500 Cypriot consumers, focusing on the factors that shape consumer environmental attitudes and behaviour, as well as on the resulting outcomes. The findings confirmed that both the inward and outward environmental attitudes of a consumer are positively influenced by his/her degree of collectivism, long-term orientation, political involvement, deontology, and law obedience, but have no connection with liberalism. The adoption of an inward environmental attitude was also found to be conducive to green purchasing behaviour that ultimately leads to high product satisfaction. On the other hand, an outward environmental attitude facilitates the adoption of a general environmental behaviour, which is responsible for greater satisfaction with life. The findings of the study have important implications for shaping effective company offerings to consumers in target markets, as well as formulating appropriate policies at the governmental level to enhance environmental sensitivity among citizens

Stabilizing organic photocathodes by low temperature atomic layer deposition of TiO2

Low-temperature atomic layer deposition forms a compact TiO2 film atop a polymer light absorber for stable and efficient organic–inorganic photo-driven H2 evolution.</p

Quantum walks: a comprehensive review

Quantum walks, the quantum mechanical counterpart of classical random walks, is an advanced tool for building quantum algorithms that has been recently shown to constitute a universal model of quantum computation. Quantum walks is now a solid field of research of quantum computation full of exciting open problems for physicists, computer scientists, mathematicians and engineers. In this paper we review theoretical advances on the foundations of both discrete- and continuous-time quantum walks, together with the role that randomness plays in quantum walks, the connections between the mathematical models of coined discrete quantum walks and continuous quantum walks, the quantumness of quantum walks, a summary of papers published on discrete quantum walks and entanglement as well as a succinct review of experimental proposals and realizations of discrete-time quantum walks. Furthermore, we have reviewed several algorithms based on both discrete- and continuous-time quantum walks as well as a most important result: the computational universality of both continuous- and discrete- time quantum walks.Comment: Paper accepted for publication in Quantum Information Processing Journa

A multi-center study on the attitudes of Malaysian emergency health care staff towards allowing family presence during resuscitation of adult patients

BACKGROUND The practice of allowing family members to witness on-going active resuscitation has been gaining ground in many developed countries since it was first introduced in the early 1990s. In many Asian countries, the acceptability of this practice has not been well studied. AIM We conducted a multi-center questionnaire study to determine the attitudes of health care professionals in Malaysia towards family presence to witness ongoing medical procedures during resuscitation. METHODS Using a bilingual questionnaire (in Malay and English language), we asked our respondents about their attitudes towards allowing family presence (FP) as well as their actual experience of requests from families to be allowed to witness resuscitations. Multiple logistic regression was used to analyze the association between the many variables and a positive attitude towards FP. RESULTS Out of 300 health care professionals who received forms, 270 responded (a 90% response rate). Generally only 15.8% of our respondents agreed to allow relatives to witness resuscitations, although more than twice the number (38.5%) agreed that relatives do have a right to be around during resuscitation. Health care providers are significantly more likely to allow FP if the procedures are perceived as likely to be successful (e.g., intravenous cannulation and blood taking as compared to chest tube insertion). Doctors were more than twice as likely as paramedics to agree to FP (p-value = 0.002). This is probably due to the Malaysian work culture in our health care systems in which paramedics usually adopt a 'follow-the-leader' attitude in their daily practice. CONCLUSION The concept of allowing FP is not well accepted among our Malaysian health care providers