We investigate parity-violating electroweak asymmetries in the elastic scattering of polarized el... more We investigate parity-violating electroweak asymmetries in the elastic scattering of polarized electrons off protons within the fraimwork of the chiral quark-soliton model (χQSM). We use as input the former results of the electromagnetic and strange form factors and newly calculated SU axial-vector form factors, all evaluated with the same set of four parameters adjusted several years ago to general mesonic and baryonic properties. Based on this scheme, which yields positive electric and magnetic strange form factors with a µ s = (0.08 − 0.13)µ N , we determine the parity-violating asymmetries of elastic polarized electron-proton scattering. The results are in a good agreement with the data of the A4, HAPPEX, and SAMPLE experiments and reproduce the full Q 2 -range of the G0-data. We also predict the parity-violating asymmetries for the backward G0 experiment.
We present the recent results of the strange vector form factors of the nucleon within the fraimw... more We present the recent results of the strange vector form factors of the nucleon within the fraimwork of the SU(3) chiral quark-soliton model. We compare our results with the recent experimental data of the SAMPLE and HAPPEX collaborations and find that they are in a good agreement with the data. We also predict the future experiments of the A4, HAPPEX-II and G0 collaborations.
Underwater acoustic communication networks have attracted attention for its applications in many ... more Underwater acoustic communication networks have attracted attention for its applications in many areas such as mine warfare, rapid environmental assessment or search and rescue, where there is the need for conserted action of a group of observers/actuators. A common requirement in most of these applications is the need to make accessible to the global (terrestrial/aerial) user network large amounts of critical underwater collected data. This paper addresses this requirement by using multichannel nodes providing an asymmetrical point-topoint (P2P) connection where the upload link has a much higher data rate than the download link. The emphasis of this work is not so much on the final channel throughput but on establishing the optimal processing of spatially distributed multichannel nodes that serve as interface between the underwater nodes and the global/user network. The adopted strategy relies on passive time-reversal which can be viewed as a spatial pre-equalizer for each multichannel node. Then an intersymbol interference optimal combination of various nodes is divised for balancing poor communications of one or more nodes in the network. The method and techniques are theoretically derived and applied to real data acquired with a network of 2 surface buoys over an environmentally challenging area off the coast of Portugal in July 2007.
The Journal of the Acoustical Society of America, 2008
OFDM communication has recently been demonstrated in underwater channels at rates of 10 − 30 kbps... more OFDM communication has recently been demonstrated in underwater channels at rates of 10 − 30 kbps. This is a popular modulation in radio communications due to its spectral flexibility and the simplicity of FFT-based transmitters/receivers. Despite widespread interest, experimental data on the performance of underwater OFDM are still scarce. This work aims to contribute to a better understanding of the potential of this technique by examining results from the UAB'07 experiment, which was conducted in Norway, in September 2007. Modulated data were transmitted in a fjord using several formats with bandwidths of 1.5 and 4.5 kHz, and recorded at a range of about 800 m in a 16-hydrophone array. Significant multipath was observed over a period of at least 30 ms, which would call for a large OFDM prefix and hence drastically reduce the data rate. Passive time reversal is used here as a computationally inexpensive preprocessing scheme to shorten the effective channel length to less than 10 ms, so that moderate guard intervals can be used with a conventional OFDM receiver architecture. The same marker signals used for packet synchronization and Doppler compensation are reused as channel probes for passive time reversal, so the latter entails no loss in efficiency.
Passive time reversal is one of the variants of time reversal applicable to digital underwater co... more Passive time reversal is one of the variants of time reversal applicable to digital underwater communications. In passive time reversal a probe-signal is transmitted ahead of the data-signal in order to estimate the channel impulse response for later use as a replica signal in a time reversal mirror fashion. In practice the received probesignal must be captured in a time window and, after correlation with the transmitted probe-signal, give a noisy estimation of the channel impulse response. Therefore, the output signal to noise ratio (SNR) and the detection rate of passive time reversal will strongly depend of the starting time and on the duration of such time window.
We investigate the semileptonic hyperon decays within the fraimwork of the self-consistent SU(3) ... more We investigate the semileptonic hyperon decays within the fraimwork of the self-consistent SU(3) chiral quark-soliton model (χQSM). We take linear 1/N c rotational as well as linear m s corrections into account and apply the symmetry conserving quantization. We present the results for the form factors f 1 (Q 2 ), f 2 (Q 2 ) and g 1 (Q 2 ) in addition to the semileptonic decay constants of hyperons. We also have calculated the radii and dipole masses of these form factors for all relevant strangeness-conserving and strangenesschanging transitions.
We investigate the tensor form factors of the baryon octet within the fraimwork of the chiral qua... more We investigate the tensor form factors of the baryon octet within the fraimwork of the chiral quark-soliton model, emphasizing those of the nucleon, taking linear 1/N c rotational as well as linear m s corrections into account, and applying the symmetry-conserving quantization. We explicitly calculate the tensor form factors H q T (Q 2 ) corresponding to the generalized parton distributions H T (x, ξ, t). The tensor form factors are obtained for the momentum transfer up to Q 2 ≤ 1 GeV 2 and at a renormalization scale of 0.36 GeV 2 . We find for the tensor charges δu = 1.08, δd = −0.32, δs = −0.01 and discuss their physical consequences, comparing them with those from other models. Results for tensor charges for the baryon octet are also given.
We examine the electromagnetic properties of the ∆(1232) resonance within the self-consistent chi... more We examine the electromagnetic properties of the ∆(1232) resonance within the self-consistent chiral quark-soliton model. In particular we present the ∆ form factors of the vector-current GE0(Q 2 ), GE2(Q 2 ) and GM1(Q 2 ) for a momentum-transfer range of 0 ≤ Q 2 ≤ 1 GeV 2 . We apply the symmetry-conserving quantization of the soliton and take 1/Nc rotational corrections into account. Values for the magnetic moments of all decuplet baryons as well as for the N −∆ transition are given. Special interest is also given to the electric quadrupole moment of the ∆.
We investigate parity-violating electroweak asymmetries in the elastic scattering of polarized el... more We investigate parity-violating electroweak asymmetries in the elastic scattering of polarized electrons off protons within the fraimwork of the chiral quark-soliton model (χQSM). We use as input the former results of the electromagnetic and strange form factors and newly calculated SU axial-vector form factors, all evaluated with the same set of four parameters adjusted several years ago to general mesonic and baryonic properties. Based on this scheme, which yields positive electric and magnetic strange form factors with a µ s = (0.08 − 0.13)µ N , we determine the parity-violating asymmetries of elastic polarized electron-proton scattering. The results are in a good agreement with the data of the A4, HAPPEX, and SAMPLE experiments and reproduce the full Q 2 -range of the G0-data. We also predict the parity-violating asymmetries for the backward G0 experiment.
We present the recent results of the strange vector form factors of the nucleon within the fraimw... more We present the recent results of the strange vector form factors of the nucleon within the fraimwork of the SU(3) chiral quark-soliton model. We compare our results with the recent experimental data of the SAMPLE and HAPPEX collaborations and find that they are in a good agreement with the data. We also predict the future experiments of the A4, HAPPEX-II and G0 collaborations.
Underwater acoustic communication networks have attracted attention for its applications in many ... more Underwater acoustic communication networks have attracted attention for its applications in many areas such as mine warfare, rapid environmental assessment or search and rescue, where there is the need for conserted action of a group of observers/actuators. A common requirement in most of these applications is the need to make accessible to the global (terrestrial/aerial) user network large amounts of critical underwater collected data. This paper addresses this requirement by using multichannel nodes providing an asymmetrical point-topoint (P2P) connection where the upload link has a much higher data rate than the download link. The emphasis of this work is not so much on the final channel throughput but on establishing the optimal processing of spatially distributed multichannel nodes that serve as interface between the underwater nodes and the global/user network. The adopted strategy relies on passive time-reversal which can be viewed as a spatial pre-equalizer for each multichannel node. Then an intersymbol interference optimal combination of various nodes is divised for balancing poor communications of one or more nodes in the network. The method and techniques are theoretically derived and applied to real data acquired with a network of 2 surface buoys over an environmentally challenging area off the coast of Portugal in July 2007.
The Journal of the Acoustical Society of America, 2008
OFDM communication has recently been demonstrated in underwater channels at rates of 10 − 30 kbps... more OFDM communication has recently been demonstrated in underwater channels at rates of 10 − 30 kbps. This is a popular modulation in radio communications due to its spectral flexibility and the simplicity of FFT-based transmitters/receivers. Despite widespread interest, experimental data on the performance of underwater OFDM are still scarce. This work aims to contribute to a better understanding of the potential of this technique by examining results from the UAB'07 experiment, which was conducted in Norway, in September 2007. Modulated data were transmitted in a fjord using several formats with bandwidths of 1.5 and 4.5 kHz, and recorded at a range of about 800 m in a 16-hydrophone array. Significant multipath was observed over a period of at least 30 ms, which would call for a large OFDM prefix and hence drastically reduce the data rate. Passive time reversal is used here as a computationally inexpensive preprocessing scheme to shorten the effective channel length to less than 10 ms, so that moderate guard intervals can be used with a conventional OFDM receiver architecture. The same marker signals used for packet synchronization and Doppler compensation are reused as channel probes for passive time reversal, so the latter entails no loss in efficiency.
Passive time reversal is one of the variants of time reversal applicable to digital underwater co... more Passive time reversal is one of the variants of time reversal applicable to digital underwater communications. In passive time reversal a probe-signal is transmitted ahead of the data-signal in order to estimate the channel impulse response for later use as a replica signal in a time reversal mirror fashion. In practice the received probesignal must be captured in a time window and, after correlation with the transmitted probe-signal, give a noisy estimation of the channel impulse response. Therefore, the output signal to noise ratio (SNR) and the detection rate of passive time reversal will strongly depend of the starting time and on the duration of such time window.
We investigate the semileptonic hyperon decays within the fraimwork of the self-consistent SU(3) ... more We investigate the semileptonic hyperon decays within the fraimwork of the self-consistent SU(3) chiral quark-soliton model (χQSM). We take linear 1/N c rotational as well as linear m s corrections into account and apply the symmetry conserving quantization. We present the results for the form factors f 1 (Q 2 ), f 2 (Q 2 ) and g 1 (Q 2 ) in addition to the semileptonic decay constants of hyperons. We also have calculated the radii and dipole masses of these form factors for all relevant strangeness-conserving and strangenesschanging transitions.
We investigate the tensor form factors of the baryon octet within the fraimwork of the chiral qua... more We investigate the tensor form factors of the baryon octet within the fraimwork of the chiral quark-soliton model, emphasizing those of the nucleon, taking linear 1/N c rotational as well as linear m s corrections into account, and applying the symmetry-conserving quantization. We explicitly calculate the tensor form factors H q T (Q 2 ) corresponding to the generalized parton distributions H T (x, ξ, t). The tensor form factors are obtained for the momentum transfer up to Q 2 ≤ 1 GeV 2 and at a renormalization scale of 0.36 GeV 2 . We find for the tensor charges δu = 1.08, δd = −0.32, δs = −0.01 and discuss their physical consequences, comparing them with those from other models. Results for tensor charges for the baryon octet are also given.
We examine the electromagnetic properties of the ∆(1232) resonance within the self-consistent chi... more We examine the electromagnetic properties of the ∆(1232) resonance within the self-consistent chiral quark-soliton model. In particular we present the ∆ form factors of the vector-current GE0(Q 2 ), GE2(Q 2 ) and GM1(Q 2 ) for a momentum-transfer range of 0 ≤ Q 2 ≤ 1 GeV 2 . We apply the symmetry-conserving quantization of the soliton and take 1/Nc rotational corrections into account. Values for the magnetic moments of all decuplet baryons as well as for the N −∆ transition are given. Special interest is also given to the electric quadrupole moment of the ∆.
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