Frequency analysis of rectangular plates continuous in one or two directions

The finite strip method is extended to the free vibration of rectangular plates continuous in one or two directions. A subroutine has been written for the computation of beam functions for continuous beams over any number of intermediate rigid supports and with simply supported or clamped end conditions. The standard finite strip method can thus be applied to plates continuous in both directions using the computed beam functions. The frequencies of 2 × 2 and 3 × 3 continuous panels with many different end conditions have been computed. The computations are also checked against published solutions and the accuracy is shown to be excellent.     

The X-ray jet and lobes of PKS 1354+195 (=4C 19.44)

We present a Chandra image of the quasar, jet, and lobes of PKS 1354+195 (=4C 19.44). The radio jet is 18 arcsec long, and appears to be very straight. The length gives many independent spatial resolution elements in the Chandra image while the straightness implies that the geometrical factors are constant along the jet although their values are uncertain. We also have 4 frequency radio images with half to one arcsecond angular resolution, and use HST and Spitzer data to study the broad band spectral energy distributions. The X-ray and radio spectra are both consistent with a spectrum f _ν ∝ ν ^−0.7 for the integrated jet. Using that spectral index, the model of inverse Compton scattering of electrons on the cosmic microwave background (IC/CMB) gives magnetic field strengths and Doppler factors that are relatively constant along the jet. Extended X-ray emission is evident in the direction of the otherwise unseen counter-jet. X-ray emission continues past the radio jet to the South, and is detected within both the southern and northern radio lobes.     

High Performance Concrete and Its Typical Mixes

- With the modern development of chemical and mineral admixtures, it is now possible to produce much higher performance concrete than before. Higher performance does not only mean higher strength, but also better durability, lower risk of thermal cracking and higher dimensional stability etc. The three most effective admixtures for producing high performance concrete are superplastieizer, pulverized fuel ash and condensed silica fume. This paper outlines the properties of these materials and presents some practical guidelines for their usage.     

Loads on a 3D body due to second-order waves and a current

Non-linear loads on a fixed body due to waves and a current are investigated. Potential theory is used to describe the flow, and a three-dimensional (3D) boundary element method (BEM), combined with a time-stepping procedure, is used to solve the problem. The exact free-surface boundary conditions are expanded about the still-water level by Taylor series so that the solution is evaluated on a time-invariant geometry. A formulation correct to second order in the wave steepness and to first order in the current speed is used. Numerical results are obtained for the first-order and the second-order oscillatory forces and for the second-order mean force on a fixed vertical circular cylinder in waves and a current. The second-order oscillatory forces on the body in waves and current are new results, while the remaining force components are verified by comparison with established numerical and analytical models. It is shown that the current can have a significant influence on the forces, and especially on the amplitude of the second-order oscillatory component.     

Optimization of buoyancy of an articulated stinger on submerged pipelines laid with a barge

An analytical method is presented for finding the elastic deflection of submerged pipelines laid with an articulated stinger in which the buoyancy of each element is adjustable. The computer time required for the method is much less than that for the finite element method, so that optimization of the laying parameters can be performed in a large region using mathematical programming. A practical example shows the efficiency of the proposed method.     

Effects of Dietary Vitamin C on the Immune Function of Shrimps, Penaeus chinensis

Prepared in this experiment were six groups of diets, i.e. VC0, VC1, VC2, VC3, VC4 and VC5 with the contents of vitamin C (VCmg(100g)-1 diet) of 0, 100, 200, 400, 800, and 1200 respectively. It was found that vitamin C increased the concentrations of immunoglobulin-like (IgG-like, IgA-like and IgM-like) substances in the serum of Penaeus chinensis after a feeding period of 3 weeks. The differences among groups were significant (P＜ 0.01), but there was no difference in the contents of complement3-1ike and complement4-1ike substances in the serum (P ＞0.05). Phenoloxidase (PO) activity in the serum of VC3 group shrimps was higher than that of VC0 and other groups, but no significant difference was observed between VC0 group and other groups. Furthermore, bactericidal activity of the serum to Vibrio parahaemolyticus in shrimps fed with the VC1 diet was higher than that in the other groups (P＜ 0.01), while no difference was demonstrated among all groups for the bactericidal activity to Vibrio alginolyticus (P ＞0.05). It is, therefore, suggested that vitamin C (100-400 mg(100 g) -1 diets) could be used as an immunostimulant of P. chinensis.     

Improved absorption cross-sections of oxygen in the wavelength region 205–240 nm of the Herzberg continuum

The laboratory values of the Herzberg continuum absorption cross-section of oxygen at room temperature from Cheung et al. (1986, Planet. Space Sci. 34, 1007), Jenouvrier et al. (1986a, Planet. Space Sci. 34, 253) and Jenouvrier et al. (1986, J. quant. Spectrosc. radiat. Transfer 36, 349) have been compared and re-analyzed. There is no discrepancy between the absolute values of these two sets of independent measurements. These values have been combined together in a linear least-squares fit to obtain improved values of the Herzberg continuum cross-section of oxygen at room temperature throughout the wavelength region 205–240 nm. Agreement with in situ and other laboratory measurements is discussed.     

香港水环境管理重点分析

With a high population density, immense commercial and industrial activities, Hong Kong produces over two million tonnes of municipal wastewater each day. Until recently, about 50% of the municipal wastewater enters water courses, rivers, and coastal waters without treatment. Untreated organics, heavy metals and refractory synthetic materials accumulate in certain areas, and have led to breakdown of aquatic and marine ecological systems, closure of beaches, red tides and bioaccumulation in seafood. In 1974, a team of consultants was commissioned to study the water pollution problems encountered in Hong Kong. After two decades in the effort to improve the water environment, a flexible framework for environmental planning and management over the following ten years has been designed. This programme comprises (1) establishment of water control zones and pollution control legislation, (2) upgrading of services and facilities for management of municipal sewage and chemical wastes, and (3) construction of the "Strategic Sewage Disposal Scheme". In line with this programme, a priority has been set on implementing a "polluter pays policy" which requires the industries to share the costs of sewage treatment and encourages them to install on-site wastewater pretreatment facilities to reduce wastewater generation and to ensure sustainable development.     

A semi-analytical boundary element method for scattering of waves in a half space

A boundary element method using finite strip discretization is proposed to investigate the three-dimensional scattering behaviour of waves in a half space. The scatterers examined are an irregular surface and a cavity in a half space. The numerical examples demonstrate the remarkably good accuracy of the results and validate the application of the present method to solve three-dimensional scattering problems.     

A data assimilation approach for groundwater parameter estimation under Bayesian maximum entropy framework

Spatial heterogeneity in groundwater system introduces significant challenges in groundwater modeling and parameter calibration. In order to mitigate the modeling uncertainty, data assiilation...