Applications of the Mild-Slope Equation to Tidal Computations in the Taiwan Strait

Employing harmonic analysis of tidal data in the Taiwan Strait, the cross-strait tidal characteristics are completely illustrated. Based on the two dimensional mild-slope equation which can be reduced to the shallow-water wave equation, a finite element model (Tsay et al., 1989) is applied to investigate the characteristics of tides in the Taiwan Strait. The co-range and equi-phase charts of major tidal constituents, such as M₂, S₂, N₂, and K₁, are reproduced. Anomalous amplification of semidiurnal tides in the Taiwan Strait is verified. With rotation effects neglected and by applying a non-reflective condition on the open boundaries, the numerical results of phase-lag and co-range distributions show very good agreement with observed data for semidiurnal tides in the Taiwan Strait. Due to crude representation of the topography at two ends along the China coast, computed tidal distributions deviate from the observations. However, both computed amplitudes and phase-lags compare very well with observed data along the central half of the China coast.     

Multiobjective optimization-based design of stabilizing piles in earth slopes

Though the technology of using stabilizing piles to prevent landsliding is not new, the design of such piles with a meaningful optimization framework has been rarely reported. In this paper, a multiobjective optimization-based framework for design of stabilizing piles is presented, in which both reinforcement effectiveness and cost efficiency could be explicitly considered. The design parameters considered in the proposed design framework are the pile parameters, including pile diameter, spacing, length, and position, and the design objectives considered are the reinforcement effectiveness and cost efficiency. The design of stabilizing piles is then implemented as a multiobjective optimization problem. In that the desire to maximize the reinforcement effectiveness and that to maximize the cost efficiency are two conflicting objectives, the output of this multiobjective optimization will be a Pareto front that depicts a trade-off between these two design objectives. With the obtained Pareto front, an informed decision regarding the design of stabilizing piles is reached. The effectiveness and significance of the proposed multiobjective optimization-based design framework for stabilizing piles are demonstrated through two illustrative examples: one is the design of stabilizing piles in a one-layer earth slope and the other the design of stabilizing piles in a two-layer earth slope. Further, parametric analyses are conducted to investigate the influences of the pile design parameters on the stability of reinforced slopes.     

Assessing CPT-based methods for liquefaction evaluation with emphasis on the cases from the Chi-Chi, Taiwan, earthquake

In the early morning (1:47 Taiwan time) of September 21, 1999, the largest earthquake of the century in Taiwan (M_w=7.6, M_L=7.3) struck this island country. The earthquake killed more than 2400 people and caused great destruction to buildings, bridges, dams, highways, and railways. One of the causes for heavy damages to the structures is soil liquefaction and ground settlement during the earthquake. In this paper, investigation of soil liquefaction and case histories of liquefaction are presented. Three CPT-based simplified methods, the Robertson method, the Olsen method, and the Juang method, are examined using the case histories derived from the Chi-Chi earthquake. The results of the comparison show that the Juang method is more accurate than the two methods in predicting liquefaction potential of soils based on the cases derived from the Chi-Chi earthquake, although all three methods are quite comparable in accuracy.     

Electrogenic capabilities of gram negative and gram positive bacteria in microbial fuel cell combined with biological wastewater treatment

The voltage and the power production of two gram negative and two gram positive bacteria in four identical continuous flow microbial fuel cells combined with biological wastewater treatment units were evaluated and compared in the present study. Each microbial fuel cell and biological treatment unit was operated at four different flow rates and four different external load resistances. The results show that overall removal efficiency of chemical oxygen demand for all four systems can reach more than 85.5 %. Each pure culture has different power generation performance that can be affected by some factors, such as wastewater characteristics, influent flow rate and hydraulic retention time of reactor. Good linear relationships between the flow rate and the potential and between the flow rate and the power density on four pure cultures at different external load resistances were found. Comamonas testosteroni has better power generation performance than Arthrobacter polychromogenes, especially at higher flow rate. Although Pseudomonas putida also showed higher power generation than Corynebacterium glutamicum, the difference was not statistically significant. It seems that gram negative bacteria could display higher power generation than gram positive bacteria at higher flow rate. However, more evidence is required to provide stronger proof for the difference of power generation between gram negative and gram positive bacteria.     

Microbial population structures in activated sludge before and after the application of synthetic polymer

Since Juang (2005) has found that the sludge settleability became much worse and the flocs displayed as pin flocs in only a few days after the addition of synthetic polymer was halted, it is hypothesized that the shift of microbial population in activated sludge before and after the addition of synthetic polymer might have occurred. Therefore, the identification of microbial population in the activated sludge of a lab-scaled continuous-flow type of treatment reactor was conducted at different phases of this study. The results of this study showed that the presence of synthetic polymer inhibited the growth of dominant bacteria and floc-formers in activated sludge, but gave a competitive advantage of growth to some other bacteria. The addition of synthetic polymer has caused the shift of microbial population and affected the growth of floc-formers in activated sludge. It took more than one month for the population structure of predominant microorganisms in activated sludge to return more closely to the initial population structure.     

Assessment of various code provisions based on optimum design of steel structures

This paper presents some comparative design results of typical structural systems in accordance with various code provisions, such as UBC and ATC-03 of the U.S. and TJ-11–78 of China. The solution comparisons are based on an optimization scheme for a given set of constraints and objective functions. Three levels of recursive procedures are employed in the algorithm to search for an optimum weight or construction cost including damages. Numerical examples are provided to compare the design results based on the aforementioned code provisions.     

Simplified procedure for reliability-based robust geotechnical design of drilled shafts in clay using spreadsheet

This paper provides a simplified procedure for reliability-based robust geotechnical design (RGD) using spreadsheet. In the RGD methodology, design robustness is achieved by adjusting “design parameters” without reducing the uncertainties in noise factors. This design approach generally involves a multi-objective optimisation, which is computationally challenging. To improve the efficiency of the RGD methodology, the design robustness is evaluated in terms of sensitivity index and the safety requirement is evaluated using mean value first order second moment (MFOSM). To ease the concern that the reliability index obtained with MFOSM may not be sufficiently accurate, a mapping function that relates MFOSM to a more accurate method such as first order reliability method is introduced. To further improve the efficiency of the proposed simplified RGD method, a new simplified procedure along with a more accurate robustness measure is developed that eliminates the need for multi-objective optimisation. With these modifications, the proposed simplified RGD method can efficiently be implemented in a single Excel spreadsheet. The proposed simplified method, which goes beyond any existing reliability-based RGD methods in terms of ease of use and computational efficiency, is illustrated in this paper with an example of robust design of drilled shaft in clay.     

Treatment of polluted river water by a gravel contact oxidation system constructed under riverbed

The objective of this study was to evaluate the treatment efficiency of a gravel contact oxidation treatment system which was newly constructed under the riverbed of Nan-men Stream located at the Shin Chu City of Taiwan. The influent and effluent water samples were taken periodically for the analyses of pH, temperature, dissolved oxygen, total suspended solids, five-day biological oxygen demand, NH₄ ⁺-N. The results showed that the average removal rates of five-day biological oxygen demand, total suspended solids and NH₄ ⁺-N were 33.6% (between ?6.7% and 82.1%), 56.3% (between ?83.0% and 93.4%) and 10.7% (between ?13.0% and 83.3%), respectively. The calculated mean first order reaction rate constant for five-day biological oxygen demand was 4.58/day with a standard deviation of 4.07/day and for NH₄ ⁺-N was 2.15/day with a standard deviation of 5.68/day. Therefore, it could be said that this gravel-contact-oxidation system could effectively remove biological oxygen demand, total suspended solids, and NH₄ ⁺-N in river water at a relatively short hydraulic retention time, although its pollutant treatment efficiency was not quite stable. However, to reach better or more stable treatment efficiency, aeration might sometimes be necessary to increase the dissolved oxygen in influent river water. And, longer hydraulic retention time of the system might also be required to increase NH₄ ⁺-N removal efficiency.     

A neural fuzzy network approach to Radar pulse compression

To make good range resolution and accuracy compatible with a high detection capability while maintaining the low average transmitted power, pulse compression processing giving low-range sidelobes is necessary. The traditional algorithms such as the direct autocorrelation filter (ACF), least squares (LS) inverse filter, and linear programming (LP) filter based on three-element Barker code (B13 code) have been developed. Recently, the neural network algorithms were issued. However, the traditional algorithms cannot achieve the requirements of high signal-to-sidelobe ratio and low integrated sidelobe level (ISL), and the normal neural networks such as the backpropagation (BP) network usually produce the extra problems of low convergence speed and are sensitive to the Doppler frequency shift. To overcome these defects, a new approach using a neural fuzzy network to deal with pulse compression in a radar system is presented. Two different Barker codes are carried out by a six-layer self-constructing neural fuzzy network (SONFIN). Simulation results show that this neural fuzzy network pulse compression (NFNPC) algorithm has significant advantages in noise rejection performance, range resolution ability, and Doppler tolerance, which are superior to the traditional and BP algorithms.     

Simplified DMT-based methods for evaluating liquefaction resistance of soils

This paper presents simplified dilatometer test (DMT)-based methods for evaluation of liquefaction resistance of soils, which is expressed in terms of cyclic resistance ratio (CRR). Two DMT parameters, horizontal stress index (K_D) and dilatometer modulus (E_D), are used as an index for assessing liquefaction resistance of soils. Specifically, CRR–K_D and CRR–E_D boundary curves are established based on the existing boundary curves that have already been developed based on standard penetration test (SPT) and cone penetration test (CPT). One key element in the development of CRR–K_D and CRR–E_D boundary curves is the correlations between K_D (or E_D) and the blow count (N) in the SPT or cone tip resistance (q_c) from the CPT. In this study, these correlations are established through regression analysis of the test results of SPT, CPT, and DMT conducted side-by-side at each of five sites selected. The validity of the developed CRR–K_D and CRR–E_D curves for evaluating liquefaction resistance is examined with published liquefaction case histories. The results of the study show that the developed DMT-based models are quite promising as a tool for evaluating liquefaction resistance of soils.