Some stability properties of large-scale baroclinic flows with nonlinear zonal current profile

The stability properties of a baroclinic zonal current with nonlinear velocity profile are investigated. The integral method is applied to the governing eigenvalue equation having the vertical velocity as the dependent variable. Expressed in terms of the Rossby number and the Richardson number, stability criteria, unstable regions in the complexc plane, and the upper bound of the unstable wave growth rate are found. Some differences in the results are noted between the present model and the quasi-geostrophic streamfunction model, particularly in connection with the effect of the velocity profile curvature termU _zz . It is conjectured in the present model that, depending on extreme behaviors ofU _zz , the propagation speed of unstable waves can be greater thanU _max or smaller thanU _min .     

Wave reflection from partially perforated-wall caisson breakwater

In 1995, Suh and Park developed a numerical model that computes the reflection of regular waves from a fully perforated-wall caisson breakwater. This paper describes how to apply this model to a partially perforated-wall caisson and irregular waves. To examine the performance of the model, existing experimental data are used for regular waves, while a laboratory experiment is conducted in this study for irregular waves. The numerical model based on a linear wave theory tends to over-predict the reflection coefficient of regular waves as the wave nonlinearity increases, but such an over-prediction is not observed in the case of irregular waves. For both regular and irregular waves, the numerical model slightly over- and under-predicts the reflection coefficients at larger and smaller values, respectively, because the model neglects the evanescent waves near the breakwater.     

Determination of palladium and platinum in seaweed

Palladium and platinum concentrations were determined for twenty two species of seaweed from the California coast, U.S.A.. A new sensitive analytical technique using atomic absorption spectrometry was developed for palladium in seaweed. For the first time, palladium contents in seaweed were obtained. The contents of palladium and platinum varied from 0.09 to 0.61 ng g^–1 and 0.25 to 1.75 ng g^–1 in dried material, respectively.The average ratio of Pt/Pd found in seaweed was 3.5, while the ratio of Pt/Pd was 4.5 in seawater. Therefore, it is postulated that there is no discrimination for seaweed to accumulate palladium and platinum from the ambient seawater due to the chemical similarity of the metals.     

Spectral analyses of solar photospheric fluctuations

Successful subtraction of instrumental background variations has permitted spectral analyses of two-dimensional measurement arrays of granulation brightness fluctuations at the center of the disk, arrays obtained from Stratoscope I, 1959B-flight, high-resolution frames B1551 and B3241.

1. RMS's, uncorrected for instrumental blurring, are 0.0850 of mean intensity for B1551 and 0.0736 for B3241, somewhat higher than other determinations. These between-frame and between-investigation differences probably result from a combination of calibration errors, frame resolution differences, and, most likely, granulation pattern differences.
2. Significant variations over each array of mean intensities and RMS's, determined for sub-arrays with dimensions in the 2500–10000 km range, indicate spatial brightness and RMS variations larger than the ‘scale’ of the granulation pattern, supporting a turbulent interpretation of photospheric convection.
3. One-dimensional power-spectra shapes provide objective and discriminating criteria for determining granulation pattern differences and, possibly, frame resolution.
4. Two-dimensional power spectra show small, essentially random deviations from axial symmetry which lie almost entirely within the 50% confidence limits.
5. Spectral densities and fluctuation power spectra, computed from the two-dimensional power spectra and corrected for instrumental blurring, noise, and blemishes, have a useable radial wavenumber range nearly double that of earlier Stratoscope I analyses.
6. Corrected RMS's obtained from the corrected fluctuation power spectra, 0.145 ± 0.046 for B1551 and 0.136 ± 0.048 for B3241, depend critically on the accuracy of the correction.
7. The spectra's wavenumber range includes the granulation-fluctuation-producing domain but not the Kolmogoroff domain of turbulence spectra.

     

Transfer of Taiwanese ideas and technology to The Gambia, West Africa: a viable approach to rural development?

The development of Taiwan's agricultural sector contributed significantly to the country's transformation from virtual poverty after World War II to a modern industrial nation. Success resulted from the use of appropriate technologies, developed through an exceptionally close working relationship between government, research and development institutions, extension services and farmers in Taiwan. As part of their overseas development aid programme, the Republic of China on Taiwan has established Technical Missions in those developing countries where it receives political recognition. Among these is The Gambia, West Africa, where one focus of Taiwan's current Technical Mission is the development of women's market gardens. Although the gardens have proved successful, there is doubt as to whether their achievements will be sustained once Taiwan's Technical Mission in The Gambia has ended. Field research in Taiwan and in The Gambia, based largely on participatory techniques, has revealed that the low-tech methods introduced from Taiwan are appropriate for the Gambian environment. However, much depends on whether women participating in the schemes can commit sufficient time and energy to the gardens, as at present this is a limiting factor. The potential of the gardens may also be constrained by a lack of appropriate institutional infrastructure, particularly the scope for profitable disposal of garden produce. A major conclusion of the article is that successful transfer of appropriate technology to The Gambia is likely to be impeded by poorly developed coordination between groups that proved to be key 'players' in the development of agriculture in Taiwan: government, research and development institutions, extension services and producers.     

Probabilistic approach for active control of structures: experimental verification

In our previous study (Earthquake Engineering and Structural Dynamics 2003; 32 :2301), we have developed a probabilistic algorithm for active control of structures. In the probabilistic control algorithm, the control force is determined by the probability that the structural energy exceeds a specified target critical energy, and the direction of a control force is determined by the Lyapunov controller design method. In this paper, an experimental verification of the proposed probabilistic control algorithm is presented. A three‐story test structure equipped with an active mass driver (AMD) has been used. The effectiveness of the control algorithm has been examined by exciting the test structure using a sinusoidal signal, a scaled El Centro earthquake and a broadband Gaussian white noise; and, especially, experiments on control have been performed under different conditions to that of system identification in order to prove the stability and robustness of the proposed control algorithm. The experimental results indicate that the probabilistic control algorithm can achieve a significant response reduction under various types of ground excitations even when the modeling error exists. Copyright © 2004 John Wiley & Sons, Ltd.     

A Review on Marine N2 Fixation: Mechanism,Evolution of Methodologies,Rates, and Future Concerns

Ocean Science Journal - Investigations on marine N2 fixation have gained momentum since 1960s with eventual establishments of relevant methodologies to identify species involved and quantify the...     

夏季对马暖流区黑潮水与陆架水的相互作用──兼论对马暖流的起源

根据1994年8月28日至9月7日韩国“Onnuri”号海洋调查船获得的CTD资料及在调查期间投放的11个卫星跟踪漂流浮标资料,分析研究了东海东北部黑潮水的分离及其与陆架水的相互作用,进而探讨了夏季的对马暖流的形成过程。