14,282 research outputs found
The behavior of quantization spectra as a function of signal-to-noise ratio
An expression for the spectrum of quantization error in a discrete-time system whose input is a sinusoid plus white Gaussian noise is derived. This quantization spectrum consists of two components: a white-noise floor and spurious harmonics. The dithering effect of the input Gaussian noise in both components of the spectrum is considered. Quantitative results in a discrete Fourier transform (DFT) example show the behavior of spurious harmonics as a function of the signal-to-noise ratio (SNR). These results have strong implications for digital reception and signal analysis systems. At low SNRs, spurious harmonics decay exponentially on a log-log scale, and the resulting spectrum is white. As the SNR increases, the spurious harmonics figure prominently in the output spectrum. A useful expression is given that roughly bounds the magnitude of a spurious harmonic as a function of the SNR
Eigenvalue extraction in NASTRAN by the tridiagonal reduction (FEER) method: Real eigenvalue analysis
The development of the tridiagonal reduction method and its implementation in NASTRAN are described for real eigenvalue analysis as typified by structural vibration and buckling problems. This method is an automatic matrix reduction scheme whereby the eigensolutions in the neighborhood of a specified point in the eigenspectrum can be accurately extracted from a tridiagonal eigenvalue problem whose order is much lower than that of the full problem. The process is effected without orbitrary lumping of masses or other physical quantities at selected node points and thus avoids one of the basic weaknesses of other techniques
Unimanual and Bimanual Weight Perception of Virtual Objects with a new Multi-finger Haptic Interface
Accurate weight perception is important particularly in tasks where the user has to apply vertical forces to ensure safe landing of a fragile object or precise penetration of a surface with a probe. Moreover, depending on physical properties of objects such as weight and size we may switch between unimanual and bimanual manipulation during a task. Research has shown that bimanual manipulation of real objects results in a misperception of their weight: they tend to feel lighter than similarly heavy objects which are handled with one hand only [8]. Effective simulation of bimanual manipulation with desktop haptic interfaces should be able to replicate this effect of bimanual manipulation on weight perception. Here, we present the MasterFinger-2, a new multi-finger haptic interface allowing bimanual manipulation of virtual objects with precision grip and we conduct weight discrimination experiments to evaluate its capacity to simulate unimanual and bimanual weight. We found that the bimanual ‘lighter’ bias is also observed with the MasterFinger-2 but the sensitivity to changes of virtual weights deteriorated
Physical Constraints to Aquatic Plant Growth in New Zealand Lakes
The nature of aquatic plant communities often defines
benthic habitat within oligotrophic and mesotrophic lakes
and lake management increasingly recognizes the importance
of maintaining plant diversity in order to sustain biological
diversity and capacity within lakes. We have developed
simple statistical relationships between key physical and vegetation
variables that define the habitat requirements, or
“habitat-templates”, of key vegetation types to facilitate management
of plant communities in New Zealand lakes. Statistical
relationships were derived from two datasets. The first
was a multi-lake dataset to determine the effects of water level
fluctuation and water clarity. The second dataset was from
a comprehensive shoreline survey of Lake Wanaka, which allowed
us to examine within-lake variables such as beach
slope and wave action. Sufficient statistical relationships were
established to develop a habitat template for each of the major
species or assemblages. The relationships suggested that
the extent and diversity of shallow-growing species was related
to a combination of the extent of water level fluctuation
and wave exposure. (PDF contains 9 pages.
Deep space network
Background, current status, and sites of Deep Space Network stations are briefly discussed
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Parameter trails
Successful communication is vital for the success of any design project. However, communication often fails, adversely affecting design process efficiency and product quality.understand the connections between different aspects of design and don–t know where to find out more information or who to talk to. This paper presents a new model, developed from current project planning techniques, which supports communication using parameter-specific data. It enables designers to question information, inform their colleagues pro-actively and assess the impact of changing parameter values on subsequent design tasks. Such interaction is critical in allowing designers to see how their own tasks fit into the overall product design
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