Software Defined Radio Implementation Of Ds-Cdma In Inter-Satellite Communications For Small Satellites

The increased usage of CubeSats recently has changed the communication philosophy from long-range point-to-point propagations to a multi-hop network of small orbiting nodes. Separating system tasks into many dispersed satellites can increase system survivability, versatility, configurability, adaptability, and autonomy. Inter-satellite links (ISL) enable the satellites to exchange information and share resources while reducing the traffic load to the ground. Establishment and stability of the ISL are impacted by factors such as the satellite orbit and attitude, antenna configuration, constellation topology, mobility, and link range. Software Defined Radio (SDR) is beginning to be heavily used in small satellite communications for applications such as base stations. A software-defined radio is a software program that does the functionality of a hardware system. The digital signal processing blocks are incorporated into the software giving it more flexibility and modulation. With this, the idea of a remote upgrade from the ground as well as the potential to accommodate new applications and future services without hardware changes is very promising. Realizing this, my idea is to create an inter-satellite link using software defined radio. The advantages of this are higher data rates, modification of operating frequencies, possibility of reaching higher frequency bands for higher throughputs, flexible modulation, demodulation and encoding schemes, and ground modifications. However, there are several challenges in utilizing the software-defined radio to create an inter-satellite link communication for small satellites. In this paper, we designed and implemented a multi-user inter-satellite communication network using SDRs, where Code Division Multiple Access (CDMA) technique is utilized to manage the multiple accesses to shared communication channel among the satellites. This model can be easily reconfigured to support any encoding/decoding, modulation, and other signal processing schemes

Software Defined Radio Implementation Of Ds-Cdma In Inter-Satellite Communications For Small Satellites

The increased usage of CubeSats recently has changed the communication philosophy from long-range point-to-point propagations to a multi-hop network of small orbiting nodes. Separating system tasks into many dispersed satellites can increase system survivability, versatility, configurability, adaptability, and autonomy. Inter-satellite links (ISL) enable the satellites to exchange information and share resources while reducing the traffic load to the ground. Establishment and stability of the ISL are impacted by factors such as the satellite orbit and attitude, antenna configuration, constellation topology, mobility, and link range. Software Defined Radio (SDR) is beginning to be heavily used in small satellite communications for applications such as base stations. A software-defined radio is a software program that does the functionality of a hardware system. The digital signal processing blocks are incorporated into the software giving it more flexibility and modulation. With this, the idea of a remote upgrade from the ground as well as the potential to accommodate new applications and future services without hardware changes is very promising. Realizing this, my idea is to create an inter-satellite link using software defined radio. The advantages of this are higher data rates, modification of operating frequencies, possibility of reaching higher frequency bands for higher throughputs, flexible modulation, demodulation and encoding schemes, and ground modifications. However, there are several challenges in utilizing the software-defined radio to create an inter-satellite link communication for small satellites. In this paper, we designed and implemented a multi-user inter-satellite communication network using SDRs, where Code Division Multiple Access (CDMA) technique is utilized to manage the multiple accesses to shared communication channel among the satellites. This model can be easily reconfigured to support any encoding/decoding, modulation, and other signal processing schemes

Bifurcation analysis of the twist-Freedericksz transition in a nematic liquid-crystal cell with pre-twist boundary conditions

Motivated by a recent investigation of Millar and McKay [Mol. Cryst. Liq. Cryst., 435, 277/[937]-286/[946] (2005)], we study the magnetic field twist-Fr´eedericksz transition for a nematic liquid crystal of positive diamagnetic anisotropy with strong anchoring and pre- twist boundary conditions. Despite the pre-twist, the system still possesses Z2 symmetry and a symmetry-breaking pitchfork bifurcation, which occurs at a critical magnetic-field strength that, as we prove, is above the threshold for the classical twist-Fr´eedericksz tran- sition (which has no pre-twist). It was observed numerically by Millar and McKay that this instability occurs precisely at the point at which the ground-state solution loses its monotonicity (with respect to the position coordinate across the cell gap). We explain this surprising observation using a rigorous phase-space analysis

HST Survey of Clusters in Nearby Galaxies. II. Statistical Analysis of Cluster Populations

We present a statistical system that can be used in the study of cluster populations. The basis of our approach is the construction of synthetic cluster color-magnitude-radius diagrams (CMRDs), which we compare with the observed data using a maximum likelihood calculation. This approach permits a relatively easy incorporation of incompleteness (a function of not only magnitude and color, but also radius), photometry errors and biases, and a variety of other complex effects into the calculation, instead of the more common procedure of attempting to correct for those effects. We then apply this procedure to our NGC 3627 data from Paper I. We find that we are able to successfully model the observed CMRD and constrain a number of parameters of the cluster population. We measure a power law mass function slope of alpha = -1.50 +/- 0.07, and a distribution of core radii centered at r_c = 1.53 +/- 0.15 pc. Although the extinction distribution is less constrained, we measured a value for the mean extinction consistent with that determined in Paper I from the Cepheids.Comment: 21 pages, 3 figures accepted for publication by A

As rotas para conduzir o processo de transição energética de baixo carbono no setor elétrico: uma análise comparativa da Alemanha e o Japão

O seguinte trabalho analisa as rotas de política pública para a conduzir a transição energética de baixo carbono desde uma perspectiva comparada dos casos da Alemanha e Japão. Para isso foi realizada uma pesquisa de qualitativa a partir do estudo comparativo de ambos os países com base na literatura sobre policy mix. Dessa forma, foi realizado um mapeamento dos pacotes de política pública adotados em cada país para conduzir a descarbonização da matriz elétrica permitindo identificar o tipo de instrumentos considerados, o escopo dos esforços governamentais implementados, e as opções tecnológicas contempladas para substituir as fontes fosseis. Entre os principais resultados, encontrou-se que as políticas de incentivo ao aumento da capacidade de geração de eletricidade a partir de fontes renováveis estão transitando de esquemas de precificação com impacto na tarifa dos consumidores para o estabelecimento de esquemas de precificação que respondam à sinais de mercado, em decorrência da redução dos custos de instalação e geração de eletricidade a partir das fontes renováveis variáveis. O estudo identificou diferenças nas opções tecnológicas consideradas para impulsionar a descarbonização, tendo como elemento notável, a desativação da geração a energia nuclear na Alemanha e a reativação dessa fonte no Japão.  Em ambos os casos, identificou-se as políticas públicas também caminham para a adaptação dos sistemas de elétricos à dinâmica das fontes renováveis variáveis. Finalmente, o escopo das políticas governamentais dos dois países almeja o impulso do desenvolvimento econômico através da construção de nova capacidade produtiva e tecnológica. The following paper analyzes the public policy paths to drive the low-carbon energy transition from a comparative perspective between the German and Japanese cases. For this purpose, qualitative research was carried out based on the comparative study between both countries and of literature about Policy Mix. Therefore, a mapping of the public policy packages adopted in each country to drive the decarbonization of the electric matrix was performed, allowing to identify the type of instruments considered, the scope of the governmental efforts implemented, and the technological options contemplated to replace fossil sources. Among the main results, it was found that the incentive policies to increase the capacity to generate electricity from renewable sources are moving from pricing schemes with an impact on the consumers' tariffs to the establishment of pricing schemes that respond to market signals, due to the reduction of the installation and electricity generation costs from variable renewable sources. The study identified differences in the technological options considered to drive decarbonization, such as phasing out nuclear power generation in Germany and its reactivation in Japan. In both cases, it was identified that public policies are also moving towards an adaptation of the electricity systems to the dynamics of variable renewable sources. Finally, the scope of the governmental policies in both countries aims at boosting economic development through the construction of new productive and technological capacity

Movimentos oculares rápidos durante o sono paradoxal em pacientes com doença cerebrovascular

Rapid eye movements that occur during paradoxical sleep are generated from the brainstem and are modulated by cerebral hemispheres. In an attempt to establish the participation of cerebral hemispheres on rapid eye movements, we carried out a quantitative study of eye movements density in patients bearing hemispheres vascular lesions. The polysomnographic recordings of 24 patients were compared to those of 24 healthy volunteers. Density of rapid eye movements was defined as the porcentage of eye movements during the respective time of paradoxical sleep. Based on the present results, we concluded that: stroke patients with hemispheric lesions displayed increased density of rapid eye movements; there was no difference on the density of rapid eye movements according to the hemispheric lesion; higher density of rapid eye movements was observed in patients with anterior hemispheric lesion.Os movimentos oculares rápidos que ocorrem durante o sono paradoxal são gerados no tronco cerebral e modulados pelos hemisférios cerebrais. Com o objetivo de estabelecer a participação dos hemisférios cerebrais no controle destes movimentos, realizamos estudo quantitativo da densidade dos movimentos oculares em pacientes com acidente vascular cerebral. O registro polissonográfico de 24 pacientes com antecedente de doença cerebrovascular foi comparado com o de 24 voluntários sadios. A densidade dos movimentos oculares rápidos foi definida como sendo a porcentagem do tempo de movimentos oculares sobre o tempo de sono paradoxal. Baseados nos resultados pudemos concluir que pacientes com acidente vascular cerebral com lesões hemisféricas mostraram aumento da densidade de movimentos oculares rápidos; não houve diferença na densidade dos movimentos oculares quanto ao hemisfério comprometido; maior densidade foi observada nos pacientes com lesões hemisféricas anteriores.Universidade Federal de São Paulo (UNIFESP) Departament of PsychobiologyUNIFESP, Departament of PsychobiologySciEL