Minimum variance estimation of galaxy power spectrum in redshift space

ABSTRACT We study an efficient way to enhance the measurability of the galaxy density and/or velocity power spectrum in redshift space. It is based on the angular decomposition with the tripolar spherical harmonic (TripoSH) basis and applicable even to galaxy distributions in wide-angle galaxy surveys. While non-trivial multipole-mode mixings are inevitable in the covariance of the Legendre decomposition coefficient commonly used in the small-angle power spectrum analysis, our analytical computation of the covariance of the TripoSH decomposition coefficient shows that such mixings are absent by virtue of high separability of the TripoSH basis, yielding the minimum variance. Via the simple signal-to-noise ratio assessment, we confirm that the detectability improvement by the TripoSH decomposition approach becomes more significant at higher multipole modes, and the hexadecapole of the density power spectrum has two orders of magnitude improvement. The TripoSH decomposition approach is expected to be applied to not only currently available survey data but also forthcoming wide-angle data, and to bring about something new or much more accurate cosmological information.

LITTER DECOMPOSITION IN Rhizophora sp. MANGROVE STANDS OF VARYING PLANTING AGES

Information about litter decomposition in Rhizophora Sp. mangrove stands of different planting ages is very important to find out the main factors affecting the whole information on structure and function of mangrove ecosystem and to improve mangrove management in the future. The objective of this study was to determine the litter decomposition in Rhizophora sp. mangrove stands of varying planting ages, with a case study in Subang Regency, West Java Province. Comparisons of litter decomposition were taken from five stands of planting ages (4 years, 12 years, 21 years, 29 years, and 38 years old). Four parameters of litter decomposition compared were dry weight of litter, decomposition rate, litter decomposition coefficient, and half-life time. The observation on Rhizophora Sp. mangrove stands was conducted in three plots of 10 m x 10 m. The results show that the litter decomposition parameters, especially dry weight of litter, decomposition rate, litter decomposition coefficient, and half-life time, were different on each planting age of Rhizophora sp. mangrove stands. The fastest time for litter decomposition was found in 12 years old of Rhizophora Sp. stands with the achievement for 90 days of observation and the decomposition efficiency of 100%. Meanwhile, the slowest was found in 38 years old of Rhizophora Sp. mangrove stands with more than 120 days, and the litter decomposition efficiency was about 97.84%. Environmental conditions (soil and water conditions, nitrogen content, and soil fauna) play a major role on its differentiation. It can be concluded that the litter decomposition in Rhizophora sp. mangrove stands of varying planting ages change over time because of the environmental conditions, but the complexity of the relation between ages is not always apparent.

Coefficient Feature Extraction and Analysis on SAR Image with Non-Subsampled Contourlet Transform

Synthetic aperture radar (SAR) can obtain remote sensing data under all-weather and all-time, but the imaging principle is very complex and the right interpretation is more difficult. In this paper, using the characteristics of non-subsampled Contourlet transform (NSCT), including multi-scale, multi direction, anisotropy and shift invariant, the microscopic analysis and extraction of multi-scale features of SAR images is fully discussed. The purpose is to supply right interpretation for SAR image applications. The practical SAR image data is decomposed by NSCT and the decomposition coefficient features are extracted and discussed.

Signal Denoising Based on Slip Threshold Value of Wavelet Packets

The signal obtained through measurement is inevitably with noise and interference. Traditional signal denoising method often takes the threshold way to process the wavelets or wavelet packets of noise signal for the purpose of denoising. Denoising by making use of slip threshold value of wavelet packets is proposed by this paper, to quantize the slip threshold value of wavelet packet decomposition coefficient, so as to obtain the reconstructed signal denoising. It is shown by the computer simulation results that the slip threshold value is with good practical value.

CQFB and PBP in Diagnosis of Local Gear Fault

The vibration signal of local gear fault is mainly composed of two components. One is the resonant signal and noise signal and the other one is the transient impulse signal including fault information. The quality factors corresponding to the two components are different. Hence, a method to diagnose local gear fault based on composite quality factor basis and parallel basis pursuit is proposed. First, two different quality factors bases are established using wavelet transform of variable quality factors to obtain the decomposition coefficient. Next, the parallel basis pursuit is adopted for the optimization of the decomposition coefficient. With the derived optimal decomposition coefficient, the resonant components with different quality factors can be reconstructed. By discussing the sparsity of signals treated with different quality factors bases, the suitable composite quality factor basis is selected to perform sparse decomposition on the signal. Besides, the obtained resonant component with low quality factor is subject to demodulation analysis, so as to derive the fault information. The feasibility and validity of the algorithm are shown by the results from simulation signal and practical application of local gear faults.

Decomposition of woody debris in Western Australian forests

Changes in mass and nutrients in experimental logs of six tree species during 5 years of exposure in the three major forest production regions of southwest Western Australia were measured to determine how climate, substrate quality, and substrate size interact to regulate decomposition of woody debris in this Mediterranean-type climate. Branch (3–5 cm in diameter) and bole (10–15 cm in diameter) material of the six species was set out in representative areas of a regenerating clear-cut Eucalyptusdiversicolor F. Muell. wet sclerophyll forest, selectively cut Eucalyptusmarginata Donn ex Smith dry sclerophyll forest, and clear-cut areas of a former Pinuspinaster Aiton plantation. Experimental logs were collected at about 0.5, 2, and 5 years after placement and were separated into bark and wood components. Samples of initial material were analyzed for moisture content, water-soluble and NaOH-soluble extractives, and nutrient concentrations (N, P, K, Ca, and Mg). At each collection, moisture content and changes in mass and nutrient concentration were determined for the sample logs. Eucalyptuscalophylla R.Br, the major associate of the two native forests, lost the most mass during this time, up to 65% of the initial mass (decomposition coefficient k = 0.22 year−1). Decomposition was least in P. pinaster and E. marginata, at about 24–26% of original mass (k = 0.05 year−1 and 0.07 year−1, respectively). Mass losses were greatest in Manjimup, the wettest site, and least at Gnangara, the driest site, but differences in overall levels of decomposition were small despite the range in climatic moisture regimes. Small logs decomposed faster than large logs. Changes in nutrient concentrations occurred in all logs at all sites, indicating activity by decomposer organisms and (or) leaching losses. Nitrogen was the only element to be immobilized over the 5-year period. Mineralization rates were of the order P ≈ Ca < Mg < K. Concentrations of compounds extractable in cold water and NaOH decreased during the 5 years of exposure. Differences in decomposition rates were partly explained by initial concentrations of N only; there appeared to be no relationship between decomposition and concentration of the other elements and extractives.