Search results for "BAND"
showing 10 items of 2610 documents
Impaired energy expenditure and physical activity in children affected by GH deficiency measured by SenseWear Armband: preliminary results.
2012
Background: Influence of growth hormone on energy expenditure and physical performance is clearly known. Objective and hypotheses: The aim of our study is to evaluate the energy expenditure (EE) during physical (PA) and sedentary activities (SA), in a group of children/adolescents affected by growth hormone deficiency (GHD) compared to healthy subjects, using an objective measure as SenseWear Armband (SWA-BodyMedia). Patients, methods and results: These preliminary data included 13 untreated, consecutive GHD children and adolescents (6 males) (GH peak 3 Mets) (1.5 ±0.8 vs 2.3±1 h/d), especially moderate (3-6 Mets)(1.4±0.8 vs 2.2±0.9 h/d; 5.8±3.1 vs 9.2±3.9% of daily hours) compared with hea…
Granular packings and fault zones
2000
The failure of a two-dimensional packing of elastic grains is analyzed using a numerical model. The packing fails through formation of shear bands or faults. During failure there is a separation of the system into two grain-packing states. In a shear band, local ``rotating bearings'' are spontaneously formed. The bearing state is favored in a shear band because it has a low stiffness against shearing. The ``seismic activity'' distribution in the packing has the same characteristics as that of the earthquake distribution in tectonic faults. The directions of the principal stresses in a bearing are reminiscent of those found at the San Andreas Fault.
The nearest X-ray emitting protostellar jet observed with HST
2009
The HH 154 jet coming from the YSO binary L1551 IRS5 is one of the closest (about 150 pc) astrophysical jet known. It is therefore a unique laboratory for studies of outflow mechanisms and of the shocks forming at the interaction front between the expanding material and the ambient medium. The substructures (knots) observed within the HH 154 jet were imaged in several spectral bands using the Hubble Space Telescope. This allows us to derive a simple characterization of the physical conditions in different structures as well as to measure the proper motion of the knots in the jet, their flux variability and shock emission over a time base of about ten years. These knots in the jet undergo si…
Propagation Channels for mmWave Vehicular Communications : State-of-the-art and Future Research Directions
2018
Vehicular communications essentially support automotive applications for safety and infotainment. For this reason, industry leaders envision an enhanced role for vehicular communications in the fifth generation of mobile communications technology. Over the years, the number of vehicle- mounted sensors has increased steadily, which potentially leads to more volume of critical data communications in a short time. Also, emerging applications such as remote/autonomous driving and infotainment such as high-definition movie streaming require data-rates on the order of multiple Gb/s. Such high data rates require a large system bandwidth, but very limited bandwidth is available in the sub-6 GHz cel…
Improving the performance of acousto-optic tunable filters in imaging applications
2010
Acousto-optic tunable filters (AOTFs) can be used as spectral filters for the implementation of multispectral imaging systems. However, obtaining quality images is challenging. In this work, we propose several improvements that enable the use of these systems in quantitative spectroscopic imaging applications. The improvements are based on three pillars: 1. a finer spectral bandpass shaping by dynamically optimizing the radio frequency (rf) driving signal, 2. an extensive calibration process, and 3. careful image preprocessing that uses calibration data to correct some well known AOTF issues in imaging applications. A novel multispectral imaging instrument is built using commercial off-the-…
Configurable Passband Imaging Spectrometer Based on Acousto-optic Tunable Filter
2008
This work presents a new configurable imaging spectrometer called Autonomous Tunable Filtering System (ATFS). The system can be configured to acquire a single narrow spectral band, a composite multispectral image, or a broad pass-band. This flexibility is given by the use of an Acousto-Optic Tunable Filter (AOTF) driven by a programmable radio frequency (rf) signal generator. The AOTF acts as a light-diffraction element which output wavelength is selected by the frequency of an rf signal applied to it. The designed rf driver is based on a high-speed Digital-to-Analog converter, which can synthesize any composite rf waveform formed by a combination of sine signals. The images are formed thro…
On the Fidelity of IEEE 802.11 commercial cards
2006
The IEEE 802.11 D CF protocol is known to be fair in terms of long-term resource repartition among the contending stations. However, when considering real scenarios, where commercial 802.11 cards interact, very unpredictable as well as sometimes surprising behaviors emerge. Motivation of this paper is to investigate the reasons of the very evident disagreement between the theoretical IEEE 802.11 DCF protocol models and its practical implementations. Inparticular, we try to characterize the card behavior not only in terms of perceived throughput, but also in terms of low-level channel access operations. In fact, the simple throughput analysis does not allow to identify what affecting paramet…
Signal-to-Noise Ratio in Bandpass Direct-Sequence Spread-Spectrum Modulation Systems
1982
The effects of a linear transmission channel on the performance of a correlator receiver for a direct-sequence spreadspectrum system are analyzed and a complete treatment of the influence of a periodic spreading code is carried out. The output data signal is obtained as a function of the channel characteristic and the code sequence employed; this allows maximizing the output signal level and evaluation of the influence of the synchronization error of the local code. The asymptotic value of the correlation loss has also been derived together with the intersymbol inteference power. The general expression of a figure of merit of the effectiveness of the system is also obtained in simple terms …
Wide bandwidth impedance meter using low rate random sampling
2008
A novel impedance measurement method based on random sampling of voltage and current signals is proposed. This technique dramatically reduces the sampling frequency requirements, thus circumventing the limitations imposed by maximum speed of the analog to digital converter and the signal processing unit. The lowering of the sampling frequencies allows the design and the implementation of an almost all digital architecture by using a simple microprocessor based embedded system and a digital frequency synthesizer. The basic principles are presented, and the implemented algorithms are described. Experimental results show the instrument performances compared to others commercial alternatives.
Multi-spectral mapping of in vivo skin hemoglobin and melanin
2010
The multi-spectral imaging technique has been used for distant mapping of in-vivo skin chromophores by analyzing spectral data at each reflected image pixel and constructing 2-D maps of the relative concentrations of oxy-/deoxyhemoglobin and melanin. Instead of using a broad visible-NIR spectral range, this study focuses on narrowed spectral band 500-700 nm, so speeding-up the signal processing procedure. Regression analysis confirmed that superposition of three Gaussians is optimal analytic approximation for the oxy-hemoglobin absorption tabular spectrum in this spectral band, while superposition of two Gaussians fits well for deoxy-hemoglobin absorption and exponential function - for mela…