Three carrier ambiguity resolution : distance-independent performance demonstrated using semi-generated triple frequency GPS signals

In spite of significant research in the development of efficient algorithms for three carrier ambiguity resolution, full performance potential of the additional frequency signals cannot be demonstrated effectively without actual triple frequency data. In addition, all the proposed algorithms showed their difficulties in reliable resolution of the medium-lane and narrow-lane ambiguities in different long-range scenarios. In this contribution, we will investigate the effects of various distance-dependent biases, identifying the tropospheric delay to be the key limitation for long-range three carrier ambiguity resolution. In order to achieve reliable ambiguity resolution in regional networks with the inter-station distances of hundreds of kilometers, a new geometry-free and ionosphere-free model is proposed to fix the integer ambiguities of the medium-lane or narrow-lane observables over just several minutes without distance constraint. Finally, the semi-simulation method is introduced to generate the third frequency signals from dual-frequency GPS data and experimentally demonstrate the research findings of this paper.

Real-time kinematic positioning over long baselines using triple-frequency BeiDou signals

The BeiDou system is the first global navigation satellite system in which all satellites transmit triple-frequency signals that can provide the positioning, navigation, and timing independently. A benefit of triple-frequency signals is that more useful combinations can be formed, including some extrawide-lane combinations whose ambiguities can generally be instantaneously fixed without distance restriction, although the narrow-lane ambiguity resolution (NL AR) still depends on the interreceiver distance or requires a long time to achieve. In this paper, we synthetically study decimeter and centimeter kinematic positioning using BeiDou triple-frequency signals. It starts with AR of two extrawide-lane signals based on the ionosphere-free or ionosphere-reduced geometry-free model. For decimeter positioning, one can immediately use two ambiguity-fixed extrawide-lane observations without pursuing NL AR. To achieve higher accuracy, NL AR is the necessary next step. Despite the fact that long-baseline NL AR is still challenging, some NL ambiguities can indeed be fixed with high reliability. Partial AR for NL signals is acceptable, because as long as some ambiguities for NL signals are fixed, positioning accuracy will be certainly improved.With accumulation of observations, more and more NL ambiguities are fixed and the positioning accuracy continues to improve. An efficient Kalman-filtering system is established to implement the whole process. The formulated system is flexible, since the additional constraints can be easily applied to enhance the model's strength. Numerical results from a set of real triple-frequency BeiDou data on a 50 km baseline show that decimeter positioning is achievable instantaneously.With only five data epochs, 84% of NL ambiguities can be fixed so that the real-time kinematic accuracies are 4.5, 2.5, and 16 cm for north, east, and height components (respectively), while with 10 data epochs more than 90% of NL ambiguities are fixed, and the rea- -time kinematic solutions are improved to centimeter level for all three coordinate components.

Assessment of code bias variations of BDS triple-frequency signals and their impacts on ambiguity resolution for long baselines

Carrier phase ambiguity resolution over long baselines is challenging in BDS data processing. This is partially due to the variations of the hardware biases in BDS code signals and its dependence on elevation angles. We present an assessment of satellite-induced code bias variations in BDS triple-frequency signals and the ambiguity resolutions procedures involving both geometry-free and geometry-based models. First, since the elevation of a GEO satellite remains unchanged, we propose to model the single-differenced fractional cycle bias with widespread ground stations. Second, the effects of code bias variations induced by GEO, IGSO and MEO satellites on ambiguity resolution of extra-wide-lane, wide-lane and narrow-lane combinations are analyzed. Third, together with the IGSO and MEO code bias variations models, the effects of code bias variations on ambiguity resolution are examined using 30-day data collected over the baselines ranging from 500 to 2600 km in 2014. The results suggest that although the effect of code bias variations on the extra-wide-lane integer solution is almost ignorable due to its long wavelength, the wide-lane integer solutions are rather sensitive to the code bias variations. Wide-lane ambiguity resolution success rates are evidently improved when code bias variations are corrected. However, the improvement of narrow-lane ambiguity resolution is not obvious since it is based on geometry-based model and there is only an indirect impact on the narrow-lane ambiguity solutions.

Geometry-free stochastic analysis of BDS triple frequency signals

The paper presents a geometry-free approach to assess the variation of covariance matrices of undifferenced triple frequency GNSS measurements and its impact on positioning solutions. Four independent geometryfree/ ionosphere-free (GFIF) models formed from original triple-frequency code and phase signals allow for effective computation of variance-covariance matrices using real data. Variance Component Estimation (VCE) algorithms are implemented to obtain the covariance matrices for three pseudorange and three carrier-phase signals epoch-by-epoch. Covariance results from the triple frequency Beidou System (BDS) and GPS data sets demonstrate that the estimated standard deviation varies in consistence with the amplitude of actual GFIF error time series. The single point positioning (SPP) results from BDS ionosphere-free measurements at four MGEX stations demonstrate an improvement of up to about 50% in Up direction relative to the results based on a mean square statistics. Additionally, a more extensive SPP analysis at 95 global MGEX stations based on GPS ionosphere-free measurements shows an average improvement of about 10% relative to the traditional results. This finding provides a preliminary confirmation that adequate consideration of the variation of covariance leads to the improvement of GNSS state solutions.

Wide area kinematic positioning with BeiDou triple frequency signals

A key challenge of wide area kinematic positioning is to overcome the effects of the varying hardware biases in code signals of the BeiDou system. Based on three geometryfree/ionosphere-free combinations, the elevation-dependent code biases are modelled for all BeiDou satellites. Results from the data sets of 30-day for 5 baselines of 533 to 2545 km demonstrate that the wide-lane (WL) integer-fixing success rates of 98% to 100% can be achieved within 25 min. Under the condition of HDOP of less than 2, the overall RMS statistics show that ionospheric-free WL single-epoch solutions achieve 24 to 50 cm in the horizontal direction. Smoothing processing over the moving window of 20 min reduces the RMS values by a factor of about 2. Considering distance-independent nature, the above results show the potential that reliable and high precision positioning services could be provided in a wide area based on a sparsely distributed ground network.

Developing regional precise positioning services using the legacy and future GNSS receivers

This paper presents an overview of technical solutions for regional area precise GNSS positioning services such as in Queensland. The research focuses on the technical and business issues that currently constrain GPS-based local area Real Time Kinematic (RTK) precise positioning services so as to operate in future across larger regional areas, and therefore support services in agriculture, mining, utilities, surveying, construction, and others. The paper first outlines an overall technical framework that has been proposed to transition the current RTK services to future larger scale coverage. The framework enables mixed use of different reference GNSS receiver types, dual- or triple-frequency, single or multiple systems, to provide RTK correction services to users equipped with any type of GNSS receivers. Next, data processing algorithms appropriate for triple-frequency GNSS signals are reviewed and some key performance benefits of using triple carrier signals for reliable RTK positioning over long distances are demonstrated. A server-based RTK software platform is being developed to allow for user positioning computations at server nodes instead of on the user's device. An optimal deployment scheme for reference stations across a larger-scale network has been suggested, given restrictions such as inter-station distances, candidates for reference locations, and operational modes. For instance, inter-station distances between triple-frequency receivers can be extended to 150km, which doubles the distance between dual-frequency receivers in the existing RTK network designs.

análise dos efeitos ionosféricos de ordem superior no ciclo solar 24 e influência no posicionamento GNSS absoluto

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Turbulence measurements in a shallow tidal estuary : analysis based on triple decomposition

In an estuary, mixing and dispersion are the result of the combination of large scale advection and small scale turbulence which are both complex to estimate. A field study was conducted in a small sub-tropical estuary in which high frequency (50 Hz) turbulent data were recorded continuously for about 48 hours. A triple decomposition technique was introduced to isolate the contributions of tides, resonance and turbulence in the flow field. A striking feature of the data set was the slow fluctuations which exhibited large amplitudes up to 50% the tidal amplitude under neap tide conditions. The triple decomposition technique allowed a characterisation of broader temporal scales of high frequency fluctuation data sampled during a number of full tidal cycles.

Spatial Demultiplexing in the sub-millimeter wave band using multlayer free-standing frequency selective surfaces

In this paper, we show that a multilayer freestanding slot array can be designed to give an insertion loss which is significantly lower than the value obtainable from a conventional dielectric backed printed frequency selective surface (FSS). This increase in filter efficiency is highlighted by comparing the performance of two structures designed to provide frequency selective beamsplitting in the quasioptical feed train of a submillimeter wave space borne radiometer. A two layer substrateless FSS providing more than 20 dB of isolation between the bands 316.5â??325.5 GHz and 349.5â??358.5 GHz, gives an insertion loss of 0.6 dB when the filter is orientated at 45 incidence in the TM plane, whereas the loss exhibited by a conventional printed FSS is in excess of 2 dB. A similar frequency response can be obtained in the TE plane, but here a triple screen structure is required and the conductor loss is shown to be comparable to the absorption loss of a dielectric backed FSS. Experimental devices have been fabricated using a precision micromachining technique. Transmission measurements performed in the range 250â??360 GHz are in good agreement with the simulated spectral performance of the individual periodic screens and the two multilayer freestanding FSS structures.

Magnetoresistance oscillations in triple quantum wells under microwave irradiation

The interference of magneto-intersubband oscillations and microwave-induced resistance oscillations is studied in high-density triple quantum wells. We give an introduction into magnetotransport in trilayer systems and focus on photoresistance measurements. The power and frequency dependence of the observed magnetoresistance oscillations can be described by the inelastic mechanism of photoresistance, generalized to the three-subband case. (C) 2009 Elsevier B.V. All rights reserved.

Investigation of Bulk and DTMOS triple-gate devices under 60 MeV proton irradiation

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Triple-aspect monism: Physiological, mental unconscious and conscious aspects of brain activity

Brain activity contains three fundamental aspects: (a) The physiological aspect, covering all kinds of processes that involve matter and/or energy; (b) the mental unconscious aspect, consisting of dynamical patterns (i.e., frequency, amplitude and phase-modulated waves) embodied in neural activity. These patterns are variously operated (transmitted, stored, combined, matched, amplified, erased, etc), forming cognitive and emotional unconscious processes and (c) the mental conscious aspect, consisting of feelings experienced in the first-person perspective and cognitive functions grounded in feelings, as memory formation, selection of the focus of attention, voluntary behavior, aesthetical appraisal and ethical judgment. Triple-aspect monism (TAM) is a philosophical theory that provides a model of the relation of the three aspects. Spatially distributed neuronal dendritic potentials generate amplitude-modulated waveforms transmitted to the extracellular medium and adjacent astrocytes, prompting the formation of large waves in the astrocyte network, which are claimed to both integrate distributed information and instantiate feelings. According to the valence of the feeling, the large wave feeds back on neuronal synapses, modulating (reinforcing or depressing) cognitive and behavioral functions.

Delays in the diagnosis of tuberculosis in a town at the triple border of Brazil, Paraguay, and Argentina

Objective. To identify the factors linked to patients and health services in delays in the diagnosis of tuberculosis. Methods. Epidemiological study in Foz do Iguacu, Parana, Brazil, 2009. The Primary Care Assessment Tool, adapted for appraising tuberculosis treatment, was the instrument used. Descriptive statistics techniques were used, such as frequency distributions, central tendency and dispersion measurements (median and interquartile intervals), and odds ratios. Results. There were greater delays in seeking health services for those in the age group 60 years and older, for females, for patients with low levels of education, and for patients with poor knowledge of the disease. Clinical variables (being a new case and HIV infection) and behavioral variables (use of tobacco and alcohol consumption) were not linked with delays in diagnosis. The median time delays before diagnosis attributable to patients and to the health services were 30 days and 10 days, respectively. Emergency 24-hour medical services and primary health care services were not effective in identifying suspicious cases of tuberculosis and requesting tests to confirm the diagnosis, with a high percentage of referrals to the Tuberculosis Control Program clinic. Conclusions. Going to primary health care services for diagnosis increased the time before diagnosis of the disease was reached. The Tuberculosis Control Program clinic was more effective in diagnosis of tuberculosis, due to the training of the staff and to an organized process for receiving patients, including the availability of tests to support the diagnosis.

Analysis of temperature variation influence on the analog performance of 45 degrees rotated triple-gate nMuGFETs

This work presents the analog performance of n-type triple-gate MuGFETs with high-k dielectrics and TiN gate material fabricated in 45 degrees rotated SOI substrates comparing their performance with standard MuGFETs fabricated without substrate rotation. Different fin widths are studied for temperatures ranging from 250 K up to 400 K. The results of transconductance, output conductance, transconductance over drain current ratio, intrinsic voltage gain and unit-gain frequency are studied. It is observed that the substrate rotation improves the carrier mobility of narrow MuGFETs at any temperature because of the changing in the conduction plane at the sidewalls from (1 1 0) to (1 0 0). For lower temperatures, the improvement of the carrier mobility of rotated MuGFETs is more noticeable as well as the rate of mobility improvement with the temperature decrease is larger. The output conductance is weakly affected by the substrate rotation. Although this improvement in the transconductance of rotated MuGFETs is negligibly transferred to the intrinsic voltage gain, the unity-gain frequency of rotated device is improved due to the larger carrier mobility in the entire range of temperatures studied. (C) 2011 Elsevier Ltd. All rights reserved.

Active immunosurveillance in the tumor microenvironment of colorectal cancer is associated with low frequency tumor budding and improved outcome.

Tumor budding (single tumor cells or small tumor cell clusters) at the invasion front of colorectal cancer (CRC) is an adverse prognostic indicator linked to epithelial-mesenchymal transition. This study characterized the immunogenicity of tumor buds by analyzing the expression of the major histocompatibility complex (MHC) class I in the invasive tumor cell compartment. We hypothesized that maintenance of a functional MHC-I antigen presentation pathway, activation of CD8+ T-cells, and release of antitumoral effector molecules such as cytotoxic granule-associated RNA binding protein (TIA1) in the tumor microenvironment can counter tumor budding and favor prolonged patient outcome. Therefore, a well-characterized multipunch tissue microarray of 220 CRCs was profiled for MHC-I, CD8, and TIA1 by immunohistochemistry. Topographic expression analysis of MHC-I was performed using whole tissue sections (n = 100). Kirsten rat sarcoma viral oncogene homolog (KRAS) and B-Raf proto-oncogene, serine/threonine kinase (BRAF) mutations, mismatch repair (MMR) protein expression, and CpG-island methylator phenotype (CIMP) were investigated. Our results demonstrated that membranous MHC-I expression is frequently down-regulated in the process of invasion. Maintained MHC-I at the invasion front strongly predicted low-grade tumor budding (P = 0.0004). Triple-positive MHC-I/CD8/TIA1 in the tumor microenvironment predicted early T-stage (P = 0.0031), absence of lymph node metastasis (P = 0.0348), lymphatic (P = 0.0119) and venous invasion (P = 0.006), and highly favorable 5-year survival (90.9% vs 39.3% in triple-negative patients; P = 0.0032). MHC-I loss was frequent in KRAS-mutated, CD8+ CRC (P = 0.0228). No relationship was observed with CIMP, MMR, or BRAF mutation. In conclusion, tumor buds may evade immune recognition through downregulation of membranous MHC-I. A combined profile of MHC-I/CD8/TIA1 improves the prognostic value of antitumoral effector cells and should be preferred to a single marker approach.