15 resultados para Constellation
Resumo:
In this letter, we propose a simple space-time code to simultaneously achieve both the space and time diversities over time dispersive channels by using two-dimensional lattice constellations and Alamouti codes. The proposed scheme still reserves full space diversity and double-real-symbols joint maximum likelihood decoding which has the similar computation complexity as the Alamouti code.
Resumo:
The inclusion of collisional rates for He-like Fe and Ca ions is discussed with reference to the analysis of solar flare Fe XXV and Ca XIX line emission, particularly from the Yohkoh Bragg Crystal Spectrometer (BCS). The new data are a slight improvement on calculations presently used in the BCS analysis software in that the discrepancy in the Fe XXV y and z line intensities (observed larger than predicted) is reduced. Values of electron temperature from satellite-to-resonance line ratios are slightly reduced (by up to 1 MK) for a given observed ratio. The new atomic data will be incorporated in the Yohkoh BCS databases. The data should also be of interest for the analysis of high-resolution, non-solar spectra expected from the Constellation-X and Astro-E space missions. A comparison is made of a tokamak S XV spectrum with a synthetic spectrum using atomic data in the existing software and the agreement is found to be good, so validating these data for particularly high-n satellite wavelengths close to the S XV resonance line. An error in a data file used for analyzing BCS Fe XXVI spectra is corrected, so permitting analysis of these spectra.
Resumo:
With the intention of introducing unique and value-added products to the market, organizations have become more conscious of how to best create knowledge as reported by Ganesh Bhatt in 2000 in 'Information dynamics, learning and knowledge creation in organizations'. Knowledge creation is recognized as having an important role in generating and sustaining a competitive advantage as well as in meeting organizational goals, as reported by Aleda Roth and her colleagues in 1994 in 'The knowledge factory for accelerated learning practices.' One of the successful ingredients of value management (VM) is its utilization of diverse knowledge resources, drawing upon different organizational functions, professional disciplines, and stakeholders, in a facilitated team process. Multidisciplinary VM study teams are viewed as having high potential to innovate due to their heterogeneous nature. This paper looks at one of the VM workshop's major benefits, namely, knowledge creation. A case study approach was used to explore the nature, processes, and issues associated with fostering a dynamic knowledge creation capability within VM teams. The results indicate that the dynamic knowledge creating process is embedded in and influenced by managing team constellation, creating shared awareness, developing shared understanding, and producing aligned action. The catalysts that can speed up the processes are open dialogue and discussion among participants. This process is enhanced by the use of facilitators, skilled at extracting knowledge.
Resumo:
This paper builds on Ferguson's important contribution to the debate on personalization in social work that appeared in the British Journal of Social Work in 2007. Whereas Ferguson approached the topic through the lens of political philosophy, the account below draws on critical social theory to examine not only the nature of personalization, but also its supportive pillar of individualization. In particular, Axel Honneth's critique of individualization in modern society is presented before setting out his ideas on the need for self-realization through inter-subjective recognition. The implications of Honneth's position are then considered in terms of four interrelated dimensions of social work practice, namely: (i) social work as symbolic interaction; (ii) social work as care; (iii) social work as respect; and (iv) social work as validation. It is argued that this constellation of practices poses a direct and necessary challenge to a social work of personalization.
Resumo:
We report the discovery by the WASP transit survey of a giant planet in a close orbit (0.0295 ± 0.0009 AU) around a moderately bright (V = 11.6, K = 10) G9 dwarf (0.89 ± 0.08 Msun, 0.84 ± 0.03 Rsun) in the Southern constellation Eridanus. Thanks to high-precision follow-up photometry and spectroscopy obtained by the telescopes TRAPPIST and Euler, the mass and size of this planet, WASP-50 b, are well constrained to 1.47 ± 0.09 MJup and 1.15 ± 0.05 RJup, respectively. The transit ephemeris is 2 455 558.6120 (±0.0002) + N × 1.955096 (±0.000005) HJDUTC. The size of the planet is consistent with basic models of irradiated giant planets. The chromospheric activity (log R'HK = -4.67) and rotational period (Prot = 16.3 ± 0.5 days) of the host star suggest an age of 0.8 ± 0.4 Gy that is discrepant with a stellar-evolution estimate based on the measured stellar parameters (?* = 1.48 ± 0.10 ?sun, Teff = 5400 ± 100 K, [Fe/H] = -0.12 ± 0.08) which favors an age of 7 ± 3.5 Gy. This discrepancy could be explained by the tidal and magnetic influence of the planet on the star, in good agreement with the observations that stars hosting hot Jupiters tend to show faster rotation and magnetic activity. We measure a stellar inclination of 84-31+6 deg, disfavoring a high stellar obliquity. Thanks to its large irradiation and the relatively small size of its host star, WASP-50 b is a good target for occultation spectrophotometry, making it able to constrain the relationship between hot Jupiters' atmospheric thermal profiles and the chromospheric activity of their host stars. The photometric time-series used in this work are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/533/A88
Resumo:
Background: This study examined dissociation, shame, guilt and intimate relationship difficulties in those with chronic and complex PTSD. Little is known about how these symptom clusters interplay within the complex PTSD constellation. Dissociation was examined as a principle organizing construct
within complex PTSD. In addition, the impact of shame, guilt and dissociation on relationship difficulties was explored.
Methods: Sixty five treatment-receiving adults attending a Northern Irish service for conflict-related trauma were assessed on measures of dissociation, state and trait shame, behavioral responses to shame, state and trait guilt, complex PTSD symptom severity and relationship difficulties.
Results: Ninety five percent (n=62) of participants scored above cut-off for complex PTSD. Those with clinical levels of dissociation (n=27) were significantly higher on complex PTSD symptom severity, state and trait shame, state guilt, withdrawal in response to shame and relationship preoccupation than subclinical dissociators (n=38). Dissociation and state and trait shame predicted complex PTSD. Fear of relationships was predicted by dissociation, complex PTSD and avoidance in response to shame, while complex PTSD predicted relationship anxiety and relationship depression.
Limitations: The study was limited to a relatively homogeneous sample of individuals with chronic and complex PTSD drawn from a single service.
Conclusions: Complex PTSD has significant consequences for intimate relationships, and dissociation makes an independent contribution to these difficulties. Dissociation also has an organizing effect on
complex PTSD symptoms.
Resumo:
Explored the facial and cry characteristics that adults use when judging an infant's pain. Sixteen women viewed videotaped reactions of 36 newborns subjected to noninvasive thigh rubs and vitamin K injections in the course of routine care and rated discomfort. The group mean interrater reliability was high. Detailed descriptions of the infants' facial reactions and cry sounds permitted specification of the determinants of distress judgments. Several facial variables (a brow bulge, eyes squeezed shut, and deepened nasolabial fold constellation, and taut tongue) accounted for 49% of the variance in ratings of affective discomfort after controlling for ratings of discomfort during a noninvasive event. In a separate analysis not including facial activity, several cry variables (formant frequency, latency to cry) also accounted for variance (38%) in ratings. When the facial and cry variables were considered together, cry variables added little to the prediction of ratings in comparison to facial variables. Cry would seem to command attention, but facial activity, rather than cry, can account for the major variations in adults' judgments of neonatal pain.
Resumo:
We propose a low-complexity closed-loop spatial multiplexing method with limited feedback over multi-input-multi-output (MIMO) fading channels. The transmit adaptation is simply performed by selecting transmit antennas (or substreams) by comparing their signal-to-noise ratios to a given threshold with a fixed nonadaptive constellation and fixed transmit power per substream. We analyze the performance of the proposed system by deriving closed-form expressions for spectral efficiency, average transmit power, and bit error rate (BER). Depending on practical system design constraints, the threshold is chosen to maximize the spectral efficiency (or minimize the average BER) subject to average transmit power and average BER (or spectral efficiency) constraints, respectively. We present numerical and Monte Carlo simulation results that validate our analysis. Compared to open-loop spatial multiplexing and other approaches that select the best antenna subset in spatial multiplexing, the numerical results illustrate that the proposed technique obtains significant power gains for the same BER and spectral efficiency. We also provide numerical results that show improvement over rate-adaptive orthogonal space-time block coding, which requires highly complex constellation adaptation. We analyze the impact of feedback delay using analytical and Monte Carlo approaches. The proposed approach is arguably the simplest possible adaptive spatial multiplexing system from an implementation point of view. However, our approach and analysis can be extended to other systems using multiple constellations and power levels.
Resumo:
In order to formalize and extend on previous ad-hoc analysis and synthesis methods a theoretical treatment using vector representations of directional modulation (DM) systems is introduced and used to achieve DM transmitter characteristics. An orthogonal vector approach is proposed which allows the artificial orthogonal noise concept derived from information theory to be brought to bear on DM analysis and synthesis. The orthogonal vector method is validated and discussed via bit error rate (BER) simulations.
Resumo:
A pattern synthesis approach is applied to a directional modulation (DM) system. A systematic synthesis procedure is suggested which ensures optimal constellation patterns production along pre-specified communication directions, whereas simultaneously conserving energy dispersal in other directions. In this study, the properties of DM systems synthesised from Gaussian magnitude far-field radiation pattern templates are used to illustrate performance benefits with regards to DM bit error rate response compared with those achieved by a conventional steered array.
Resumo:
Directional modulation (DM) is a recently introduced technique for secure wireless transmission using direct physical layer wave-front manipulation. This paper provides a bit error rate (BER)-based DM array synthesis method. It is shown for the first time that the standard constellation mappings in In-phase and Quadrature (IQ) space to a pre-specified BER can be exactly achieved along a given specified spatial direction. Different receiver capabilities are investigated and different assessment metrics for each case are discussed. The approach is validated for a 1 × 4 element dipole array operating at 1 GHz.
Resumo:
A 10 GHz Fourier Rotman lens enabled dynamic directional modulation (DM) transmitter is experimentally evaluated. Bit error rate (BER) performance is obtained via real-time data transmission. It is shown that Fourier Rotman DM functionality enhances system security performance in terms of narrower decodable low BER region and higher BER values associated with BER sidelobes especially under high signal to noise ratio (SNR) scenarios. This enhancement is achieved by controlled corruption of constellation diagrams in IQ space by orthogonal injection of interference. Furthermore, the paper gives the first report of a functional dual-beam DM transmitter, which has the capability of simultaneously projecting two independent data streams into two different spatial directions while simultaneously scrambling the information signals along all other directions.
Resumo:
Passive intermodulation (PIM) often limits the performance of communication systems with analog and digitally-modulated signals and especially of systems supporting multiple carriers. Since the origins of the apparently multiple physical sources of nonlinearity causing PIM are not fully understood, the behavioral models are frequently used to describe the process of PIM generation. In this paper a polynomial model of memoryless nonlinearity is deduced from PIM measurements of a microstrip line with distributed nonlinearity with two-tone CW signals. The analytical model of nonlinearity is incorporated in Keysight Technology’s ADS simulator to evaluate the metrics of signal fidelity in the receive band for analog and digitally-modulated signals. PIM-induced distortion and cross-band interference with modulated signals are compared to those with two-tone CW signals. It is shown that conventional metrics can be applied to quantify the effect of distributed nonlinearities on signal fidelity. It is found that the two-tone CW test provides a worst-case estimate of cross-band interference for two-carrier modulated signals whereas with a three-carrier signal PIM interference in the receive band is noticeably overestimated. The simulated constellation diagrams for QPSK signals demonstrate that PIM interference exhibits the distinctive signatures of correlated distortion and this indicates that there are opportunities for mitigating PIM interference and that PIM interference cannot be treated as noise. One of the interesting results is that PIM distortion on a transmission line results in asymmetrical regrowth of output PIM interference for modulated signals.
Resumo:
Objectives: Elevated shame and dissociation are common in dissociative identity disorder (DID) and chronic posttraumatic stress disorder (PTSD) and are part of the constellation of symptoms defined as complex PTSD. Previous work examined the relationship between shame, dissociation, and complex PTSD and whether they are associated with intimate relationship anxiety, relationship depression, and fear of relationships. This study investigated these variables in traumatized clinical samples and a nonclinical community group.
Method: Participants were drawn from the DID (n = 20), conflict-related chronic PTSD (n = 65), and nonclinical (n = 125) populations and completed questionnaires assessing the variables of interest. A model examining the direct impact of shame and dissociation on relationship functioning, and their indirect effect via complex PTSD symptoms, was tested through path analysis.
Results: The DID sample reported significantly higher dissociation, shame, complex PTSD symptom severity, relationship anxiety, relationship depression, and fear of relationships than the other two samples. Support was found for the proposed model, with shame directly affecting relationship anxiety and fear of relationships, and pathological dissociation directly affecting relationship anxiety and relationship depression. The indirect effect of shame and dissociation via complex PTSD symptom severity was evident on all relationship variables.
Conclusion: Shame and pathological dissociation are important for not only the effect they have on the development of other complex PTSD symptoms, but also their direct and indirect effects on distress associated with relationships.