Background: Functional connectomes (FCs) have been shown to provide a reproducible individual fingerprint, which has opened the possibility of personalized medicine for neuro/psychiatric disorders. Thus, developing accurate ways to compare FCs is essential to establish associations with behavior and/or cognition at the individual level. Methods: Canonically, FCs are compared using Pearson's correlation coefficient of the entire functional connectivity profiles. Recently, it has been proposed that the use of geodesic distance is a more accurate way of comparing FCs, one which reflects the underlying non-Euclidean geometry of the data. Computing geodesic distance requires FCs to be positive-definite and hence invertible matrices. As this requirement depends on the functional magnetic resonance imaging scanning length and the parcellation used, it is not always attainable and sometimes a regularization procedure is required. Results: In the present work, we show that regularization is not only an algebraic operation for making FCs invertible, but also that an optimal magnitude of regularization leads to systematically higher fingerprints. We also show evidence that optimal regularization is data set-dependent and varies as a function of condition, parcellation, scanning length, and the number of frames used to compute the FCs. Discussion: We demonstrate that a universally fixed regularization does not fully uncover the potential of geodesic distance on individual fingerprinting and indeed could severely diminish it. Thus, an optimal regularization must be estimated on each data set to uncover the most differentiable across-subject and reproducible withinsubject geodesic distances between FCs. The resulting pairwise geodesic distances at the optimal regularization level constitute a very reliable quantification of differences between subjects.
This letter proposes a scheme for the format conversion of on-off keying (OOK) signal to quadrature phase-shift keying (QPSK) and 16-ary quadrature amplitude modulation (16QAM) signals via cross-phase modulation (XPM) in a semiconductor optical amplifier (SOA). Theoretical and experimental analyses of the format conversion scheme are conducted to validate its feasibility. The phase changing is obtained because of the XPM in the SOA. The QPSK and 16QAM signals are converted from the OOK signal. The performance of the 10 Gb/s format conversion system is evaluated and discussed. The receiver sensitivities of the converted QPSK and 16QAM signals after detection are -27.25 and -23.5 dBm, respectively, at a bit error rate (BER) of 10 −9 . OCIS codes: 060.2330, 230.4480, 070.4340. doi: 10.3788/COL201311.030604.All-optical signal processing is a promising technology for future optical transparent networks because it helps reduce implementation costs and removes the bottleneck in ultrafast signal processing without requiring costly optical-electrical-optical equipment [1,2] . Optical format conversion, one of the key optical signal processing technologies, has been extensively studied. Researchers have mainly focused on the conversion between conventional on-off keying (OOK) and binary phase shift keying (BPSK) [3−6] . By contrast, the multiple-OOK to M -ary phase-shift keying and/or quadrature amplitude modulation (QAM) conversion is rarely demonstrated. The OOK to BPSK conversion can be conducted in commercially available semiconductor optical amplifier (SOA) because of the simplicity of the BPSK format. However, the conversion of multiple OOK signals to higher order constellation signals is more difficult to achieve and requires a more flexible device approach than that of a single SOA. Based on previous reports, schemes are usually complex and costly, such as cascaded Mach-Zehnder modulators (MZMs) followed by a phase modulator [7] , dual-parallel MZM [8] , dual-drive MZM [9] , and parallel SOA Mach-Zehnder interferometer (MZI) [10] . In this letter, a novel scheme for the format conversion of nonreturn to zero (NRZ)-OOK signal to QPSK or 16-ary QAM (16QAM) signal via cross-phase modulation (XPM) in a SOA based MZI (SOA-MZI) is proposed and verified. The return to zero (RZ) pulse and dual NRZ-OOK signals are injected into a SOA, and the quadrature phase-shift keying (QPSK) signal is converted from an OOK signal via the XPM in the SOA. The dual NRZ-OOK signals are then injected into the SOAs located at the upper and lower MZI arm. Therefore, the dual QPSK signal is converted at the lower and upper arm via the XPM in the SOA-MZI. The 16QAM signal can then be converted by coupling the double QPSK signals. The scheme is simpler, more compact, and cost-efficient than traditional schemes. Our format conversion scheme is entirely in the optical domain and reduces the unstable factors in the electrical domain. The feasibility of this technique is evaluated through theoretical and experimental analyses. Figure 1 shows the th...
Detecting communities problems have been studied under various background and networks in last two decades. This paper poses a new problem, named community detection with noise, to find communities where nodes connect densely to each other under the background of user movement in 5G. Because the prospective small cells in 5G would make data lengthy [1] [2], this paper aims to figure out meaningful areas without seldom visited cells named as "noise". Two kinds of methods are proposed. One is based on the normal community detection problem. Noise nodes are picked and deleted by proper quantities. The other is a heuristic algorithm that starts with the most important node, adding closely connected nodes into the community. Compared with classic GN algorithm, these two methods outperform in quality metrics that focus on internal density. And a practical example that gives user movement areas is showed.
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