Nonparametric identification of a class of nonlinear close-coupled dynamic systems

A nonparametric identification technique for the identification of close coupled dynamic systems with arbitrary memoryless nonlinearities is presented. The method utilizes noisy recorded data (acceleration, velocity and displacement) to identify the restoring forces in the system. The masses in the system are assumed to be known (or fairly well estimated from the design drawings). The restoring forces are expanded in a series of orthogonal polnomials and the coefficients of these polynomial expansions are obtained by using least square fit method. A particularly simple and computationally efficient method is proposed for dealing with separable restoring forces. The identified results are found to be relatively insensitive to measurement noise. An analysis of the effects of measurement noise on the quality of the estimates is given. The computations are shown to be relatively quick (when compared say to the Wiener identification method) and the core storage required relatively small, making the method suitable for onboard identification of large space structures

On the use of colour reflectivity plots to monitor the structure of the troposphere and stratosphere

The radar reflectivity, defined as the range squared corrected power of VHF radar echoes, can be used to monitor and study the temporal development of inversion layer, frontal boundaries and convective turbulence. From typical featurs of upward or downward motion of reflectivity structures, the advection/convection of cold and warm air can be predicted. High resolution color plots appear to be useful to trace and to study the life history of these structures, particularly their persistency, descent and ascent. These displays allow an immediate determination of the tropopause height as well as the determination of the tropopause structure. The life history of warm fronts, cold fronts, and occlusions can be traced, and these reflectivity plots allow detection of even very weak events which cannot be seen in the traditional meteorological data sets. The life history of convective turbulence, particular evolving from the planetary boundary layer, can be tracked quite easily. Its development into strong convection reaching the middle troposphere can be followed and predicted

Glueball matrix elements on anisotropic lattices

We describe a lattice calculation of the matrix elements relevant for glueball production in $J / \psi$ radiative decays. The techniques for such a calculation on anisotropic lattices with an improved action are outlined. We present preliminary results showing the efficacy of the computational method.Comment: 3 pages (LaTeX), 3 figures (PostScript), Presented at Lattice '9

The first operation and results of the Chung-Li VHF radar

The Chung-Li Very High Frequency (VHF) radar is used in the dual-mode operations, applying Doppler beam-swinging as well as the spaced-antenna-drift method. The design of the VHF radar is examined. Results of performance tests are discussed

Hermitian quark mass matrices with four texture zeros

We provide a complete and systematic analysis of hermitian, hierarchical quark mass matrices with four texture zeros. Using triangular mass matrices, each pattern of texture zeros is readily shown to lead to a definite relation between the CKM parameters and the quark masses. Nineteen pairs are found to be consistent with present data, and one other is marginally acceptable. In particular, no parallel structure between the up and down mass matrices is found to be favorable with data.Comment: 18 pages, no figure, references [8] and [10] adde

Phase and group velocity tracing analysis of projected wave packet motion along oblique radar beams ? qualitative analysis of QP echoes

International audienceThe wave packets of atmospheric gravity waves were numerically generated, with a given characteristic wave period, horizontal wave length and projection mean wind along the horizontal wave vector. Their projection phase and group velocities along the oblique radar beam (vpr and vgr), with different zenith angle ? and azimuth angle ?, were analyzed by the method of phase- and group-velocity tracing. The results were consistent with the theoretical calculations derived by the dispersion relation, reconfirming the accuracy of the method of analysis. The RTI plot of the numerical wave packets were similar to the striation patterns of the QP echoes from the FAI irregularity region. We propose that the striation range rate of the QP echo is equal to the radial phase velocity vpr, and the slope of the energy line across the neighboring striations is equal to the radial group velocity vgr of the wave packet; the horizontal distance between two neighboring striations is equal to the characteristic wave period ?. Then, one can inversely calculate all the properties of the gravity wave responsible for the appearance of the QP echoes. We found that the possibility of some QP echoes being generated by the gravity waves originated from lower altitudes cannot be ruled out

Coupled valence and spin state transition in (Pr0.7Sm0.3)0.7Ca0.3CoO3

The coupled valence and spin state transition (VSST) taking place in (Pr0.7Sm0.3)0.7Ca0.3CoO3 was investigated by soft x-ray absorption spectroscopy (XAS) experiments carried out at the Pr-M4,5, Co-L2,3, and O-1s edges. This VSST is found to be composed of a sharp Pr/Co valence and Co spin state transition centered at T*=89.3 K, followed by a smoother Co spin-state evolution at higher temperatures. At T < T*, we found that the praseodymium displays a mixed valence Pr3+/Pr4+ with about 0.13 Pr4+/f.u., while all the Co3+ is in the low-spin (LS) state. At T around T*, the sharp valence transition converts all the Pr4+ to Pr3+ with a corresponding Co3+ to Co4+ compensation. This is accompanied by an equally sharp spin state transition of the Co3+ from the low to an incoherent mixture of low and high spin (HS) states. An involvement of the intermediate spin (IS) state can be discarded for the Co3+. While above T* and at high temperatures the system shares rather similar properties as Sr-doped LaCoO3, at low temperatures it behaves much more like EuCoO3 with its highly stable LS configuration for the Co3+. Apparently, the mechanism responsible for the formation of Pr4+ at low temperatures also helps to stabilize the Co3+ in the LS configuration despite the presence of Co4+ ions. We also found out that that the Co4+ is in an IS state over the entire temperature range investigated in this study (10-290 K). The presence of Co3+ HS and Co4+ IS at elevated temperatures facilitates the conductivity of the material.Comment: 19 pages, 7 figures, Accepted in PR

Resistance and resilience of social–ecological systems to recurrent typhoon disturbance on a subtropical island: Taiwan

Tropical cyclones (TCs) have major effects on ecological and social systems. However, studies integrating the effects of TCs on both social and ecological systems are rare, especially in the northwest Pacific, where the frequency of TCs (locally named typhoons) is the highest in the world. We synthesized studies of effects of recurrent typhoons on social and ecological systems in Taiwan over the last several decades. Many responses to TCs are comparable between social and ecological systems. High forest ecosystem resistance, evident from tree mortality below 2% even following multiple strong typhoons, is comparable with resistance of social systems, including the only 4% destruction of river embankments following a typhoon that brought nearly 3000 mm rainfall in three days. High resilience as reflected by quick returns of leaf area index, mostly in one year, and streamwater chemistry, one to several weeks to pre‐typhoon levels of ecosystems, are comparable to quick repair of the power grid within one to several days and returns of vegetable price within several weeks to pre‐typhoon levels of the social systems. Landslides associated with intense typhoons have buried mountain villages and transported large quantities of woody debris to the coast, affecting the coastal plains and reefs, illustrating a ridge‐to‐reef link between ecological and societal systems. Metrics of both social and ecological function showed large fluctuations in response to typhoons but quickly returned to pre‐disturbance levels, except when multiple intense typhoons occurred within a single season. Our synthesis illustrates that the social–ecological systems in Taiwan are highly dynamic and responsive to frequent typhoon disturbance, with extraordinarily high resistance and resilience. For ecosystems, the efficient responsiveness results from the selective force of TCs on ecosystem structure and processes. For social systems, it is the result of the effects of TCs on planning and decision making by individuals (e.g., farmers), management sectors, and ultimately the government. In regions with frequent TCs, the social–ecological systems are inevitably highly dynamic and rapid responses are fundamental to system resistance and resilience which in turn is key to maintaining structure and function of the social–ecological systems