467 research outputs found
Interference Cancellation Using Power Minimization and Self-coherence Properties of GPS Signals
This paper presents the performance analysis of two digital beam forming techniques used in conjunction with a software GPS receiver to mitigate interference to GPS signals in interference environment. The first method is the constrained minimum power (MOP) method. The second method is the so-called self-coherence restoral (SCORE) method. Both experimental and simulation data are used in the study. The study was performed using experiment data collected in an anechoic chamber to obtain GPS and interference signals. A two by two GPS antenna array and a four channel radio frequency front end were used to collect simulated GPS data generated using hardwarebased simulator in controlled interference environment. Three types of interference signals are deployed in the experiments: FM chirp, binary phase shift key, and broadband. The interference power levels used were +20, +30, and +40 dB above GPS signal power. A software GPS receiver was used to perform acquisition of GPS signals to evaluate the performance of the beam forming algorithms. The preliminary result showed that the MOP method can effectively mitigate all three types of interference at all power levels if a single interference source is present. Experiments using multiple broadband interference sources were also analyzed and our results shown that the effectiveness of the MOP method diminishes as the interference signal power increases and ceases to function at the +40 dB level. The SCORE method does not exhibit consistent performance for the experimental data. This is consistent with our simulation results which show that for the SCORE algorithm to generate satisfactory results, sufficient number of antenna elements is necessary even if there is no interference source present. The number of antenna element is determined by the number of satellites available, as well as the number of interference sources. The experimental and simulation results are discussed in this paper
Spin diffusion in -type (111) GaAs quantum wells
We utilize the kinetic spin Bloch equation approach to investigate the
steady-state spin diffusion in -type (111) GaAs quantum wells, where the
in-plane components of the Dresselhaus spin-orbit coupling term and the Rashba
term can be partially canceled by each other. A peak of the spin diffusion
length due to the cancellation is predicted in the perpendicular electric field
dependence. It is shown that the spin diffusion length around the peak can be
markedly controlled via temperature and doping. When the electron gas enters
into the degenerate regime, the electron density also leads to observable
influence on the spin diffusion in the strong cancellation regime. Furthermore,
we find that the spin diffusion always presents strong anisotropy with respect
to the direction of the injected spin polarization. The anisotropic spin
diffusion depends on whether the electric field is far away from or in the
strong cancellation regime.Comment: 5 pages, 3 figures, to be published in Solid State Commu
Detection of herb-symptom associations from traditional chinese medicine clinical data
YesTraditional Chinese medicine (TCM) is an individualized medicine by observing the symptoms and signs (symptoms in brief) of patients. We aim to extract the meaningful herb-symptom relationships from large scale TCM clinical data. To investigate the correlations between symptoms and herbs held for patients, we use four clinical data sets collected from TCM outpatient clinical settings and calculate the similarities between patient pairs in terms of the herb constituents of their prescriptions and their manifesting symptoms by cosine measure. To address the large-scale multiple testing problems for the detection of herb-symptom associations and the dependence between herbs involving similar efficacies, we propose a network-based correlation analysis (NetCorrA) method to detect the herb-symptom associations. The results show that there are strong positive correlations between symptom similarity and herb similarity, which indicates that herb-symptom correspondence is a clinical principle adhered to by most TCM physicians. Furthermore, the NetCorrA method obtains meaningful herb-symptom associations and performs better than the chi-square correlation method by filtering the false positive associations. Symptoms play significant roles for the prescriptions of herb treatment. The herb-symptom correspondence principle indicates that clinical phenotypic targets (i.e., symptoms) of herbs exist and would be valuable for further investigations
Changes in chronic medication adherence, costs, and health care use after a cancer diagnosis among low-income patients and the role of patient-centered medical homes
Background: Approximately 40% of patients with cancer also have another chronic medical condition. Patient-centered medical homes (PCMHs) have improved outcomes among patients with multiple chronic comorbidities. The authors first evaluated the impact of a cancer diagnosis on chronic medication adherence among patients with Medicaid coverage and, second, whether PCMHs influenced outcomes among patients with cancer. Methods: Using linked 2004 to 2010 North Carolina cancer registry and claims data, the authors included Medicaid enrollees who were diagnosed with breast, colorectal, or lung cancer who had hyperlipidemia, hypertension, and/or diabetes mellitus. Using difference-in-difference methods, the authors examined adherence to chronic disease medications as measured by the change in the percentage of days covered over time among patients with and without cancer. The authors then further evaluated whether PCMH enrollment modified the observed differences between those patients with and without cancer using a differences-in-differences-in-differences approach. The authors examined changes in health care expenditures and use as secondary outcomes. Results: Patients newly diagnosed with cancer who had hyperlipidemia experienced a 7-percentage point to 11-percentage point decrease in the percentage of days covered compared with patients without cancer. Patients with cancer also experienced significant increases in medical expenditures and hospitalizations compared with noncancer controls. Changes in medication adherence over time between patients with and without cancer were not determined to be statistically significantly different by PCMH status. Some PCMH patients with cancer experienced smaller increases in expenditures (diabetes) and emergency department use (hyperlipidemia) but larger increases in their inpatient hospitalization rates (hypertension) compared with non-PCMH patients with cancer relative to patients without cancer. Conclusions: PCMHs were not found to be associated with improvements in chronic disease medication adherence, but were associated with lower costs and emergency department visits among some low-income patients with cancer
Interplay between edge states and simple bulk defects in graphene nanoribbons
We study the interplay between the edge states and a single impurity in a
zigzag graphene nanoribbon. We use tight-binding exact diagonalization
techniques, as well as density functional theory calculations to obtain the
eigenvalue spectrum, the eigenfunctions, as well the dependence of the local
density of states (LDOS) on energy and position. We note that roughly half of
the unperturbed eigenstates in the spectrum of the finite-size ribbon hybridize
with the impurity state, and the corresponding eigenvalues are shifted with
respect to their unperturbed values. The maximum shift and hybridization occur
for a state whose energy is inverse proportional to the impurity potential;
this energy is that of the impurity peak in the DOS spectrum. We find that the
interference between the impurity and the edge gives rise to peculiar
modifications of the LDOS of the nanoribbon, in particular to oscillations of
the edge LDOS. These effects depend on the size of the system, and decay with
the distance between the edge and the impurity.Comment: 10 pages, 15 figures, revtex
Direct Measurements of the Branching Fractions for and and Determinations of the Form Factors and
The absolute branching fractions for the decays and
are determined using singly
tagged sample from the data collected around 3.773 GeV with the
BES-II detector at the BEPC. In the system recoiling against the singly tagged
meson, events for and events for decays are observed. Those yield
the absolute branching fractions to be and . The
vector form factors are determined to be
and . The ratio of the two form
factors is measured to be .Comment: 6 pages, 5 figure
Measurements of J/psi Decays into 2(pi+pi-)eta and 3(pi+pi-)eta
Based on a sample of 5.8X 10^7 J/psi events taken with the BESII detector,
the branching fractions of J/psi--> 2(pi+pi-)eta and J/psi-->3(pi+pi-)eta are
measured for the first time to be (2.26+-0.08+-0.27)X10^{-3} and
(7.24+-0.96+-1.11)X10^{-4}, respectively.Comment: 11 pages, 6 figure
BESII Detector Simulation
A Monte Carlo program based on Geant3 has been developed for BESII detector
simulation. The organization of the program is outlined, and the digitization
procedure for simulating the response of various sub-detectors is described.
Comparisons with data show that the performance of the program is generally
satisfactory.Comment: 17 pages, 14 figures, uses elsart.cls, to be submitted to NIM
Measurement of branching fractions for the inclusive Cabibbo-favored ~K*0(892) and Cabibbo-suppressed K*0(892) decays of neutral and charged D mesons
The branching fractions for the inclusive Cabibbo-favored ~K*0 and
Cabibbo-suppressed K*0 decays of D mesons are measured based on a data sample
of 33 pb-1 collected at and around the center-of-mass energy of 3.773 GeV with
the BES-II detector at the BEPC collider. The branching fractions for the
decays D+(0) -> ~K*0(892)X and D0 -> K*0(892)X are determined to be BF(D0 ->
\~K*0X) = (8.7 +/- 4.0 +/- 1.2)%, BF(D+ -> ~K*0X) = (23.2 +/- 4.5 +/- 3.0)% and
BF(D0 -> K*0X) = (2.8 +/- 1.2 +/- 0.4)%. An upper limit on the branching
fraction at 90% C.L. for the decay D+ -> K*0(892)X is set to be BF(D+ -> K*0X)
< 6.6%
Search for the Lepton Flavor Violation Processes and
The lepton flavor violation processes and are
searched for using a sample of 5.8 events collected with
the BESII detector. Zero and one candidate events, consistent with the
estimated background, are observed in and
decays, respectively. Upper limits on the branching ratios are determined to be
and at the 90% confidence level (C.L.).Comment: 9 pages, 2 figure
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