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.     

A preliminary study on Typhoon Tim induced resonance at Hualien Harbor,Taiwan

New analysis of wave records at Hualien Harbor during Typhoon Tim in 1994 reveals that for certain wave periods, the ratios of measured wave heights among three available wave stations inside the harbor are unique and roughly remain the same during the severest period of resonance. Since there is no incident infragravity wave (period from 80 to 220 s) information at offshore boundaries, these unique ratios become the surrogate of background truth for checking the performance of numerical simulations. A new simulation effort using a large (45 × 17 km) modeling domain, high-resolution (20 × 20 m) grid and the RIDE wave transformation model were conducted to simulate the observed responses. Comparison of the modeling results with the observations showed reasonable agreement. Additional model studies using ideal bathymetries with the same grid domain and resolution were also conducted to help interpret the prototype modeling results. The effects of two types of commonly used remedies were first examined by using the ideal bathymetry, and then, the prototype bathymetry. The results demonstrated that a single 1-km long, shore-parallel breakwater could significantly reduce the resonance. The results of using three shore-parallel breakwaters, however, are no better. More studies to identify the optimum design associated with the shore-parallel breakwater (location, length, etc.) are necessary for the optimum reduction of resonance at Hualien Harbor.     

Noise pollution and its effects on medical care workers and patients in hospitals

The objectives of this study are to investigate the levels of noise pollution in some hospitals in Taiwan and to study the effects of noise pollution on the physiological and psychological reactions and annoyance response of medical care staff, patients and visitors in these hospitals. An instrument for the measurement of sound level was used and a self-answered survey questionnaire on noise pollution was administered. Results showed that the daily average sound levels measured inside these hospitals during daytime were between 52.6 and 64.6 decibels. These are higher than the current daytime environmental noise limit of 50 decibels in Taiwan. Most nursing staff members expressed that “talking of visitors or patient’s family members” is the major source of noise inside the wards, whereas “talking of visitors or patient’s family members” and “children playing” are the two major noise sources outside the wards. However, most patients or visitors claimed that “doors opening or closing” and “patients moaning or crying” are the two major sources of noise inside the wards. “Footsteps,” “renovation of hospitals,” “talking of visitors or patient’s family members,” “shouting of nursing staff” and “doors opening or closing” are the five major noise sources outside the wards. To conclude, noise pollution inside and outside the wards either directly or indirectly affects, in a simultaneous manner, the subjective perception of noise, emotions, physiology and experience of noise inside and outside the wards of both the medical care staff and the patients and visitors.     

Framework for assessing probability of exceeding a specified liquefaction-induced settlement at a given site in a given exposure time

This paper presents a framework for assessing the probability of exceeding a specified liquefaction-induced settlement at a given site in a given exposure time. This framework deals not only with the effect of liquefaction (in terms of settlement) but also with probabilistic characterization of all possible ground motions at a given site (in terms of a joint distribution of a_max and M_w). Additionally, a new concept, referred to herein as liquefaction-induced settlement hazard curve, is introduced for assessing the annual rate of settlement exceedance at a given site. This settlement hazard curve concept has the potential to be a very useful tool in the field of geotechnical earthquake engineering. Satisfactory results are obtained in the demonstration examples analyzed with the proposed framework. Whereas the proposed framework is simple and effective, further refinements to this framework, especially on the treatment of epistemic uncertainty, are warranted.     

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.     

Anomalous amplifications of semidiurnal tides along the western coast of Taiwan

By compiling all the tidal data gathered from island-wide results of simple harmonic analysis, anomalous amplifications of semidiurnal tides along the western coast of Taiwan are illustrated. The mechanisms are investigated both theoretically and numerically by applying the linear shallow-water wave equations. Waves trapped by a continental shelf and resonance of tidal co-oscillation are identified theoretically. Numerically, a two-dimensional finite element model is applied to real topography for tidal computations. The co-range and equi-phase charts of three main semidiurnal constituents (M₂, S₂, and N₂) and one diurnal constituent K₁ are calculated. Anomalous amplifications of semidiurnal tides that appear as partially standing waves are demonstrated.     

A practical reliability-based method for assessing soil liquefaction potential

The current simplified methods for assessing soil liquefaction potential use a deterministic safety factor in order to judge whether liquefaction will occur or not. However, these methods are unable to determine the liquefaction probability related to a safety factor. An answer to this problem can be found by reliability analysis. This paper presents a reliability analysis method based on the popular Seed'85 liquefaction analysis method. This reliability method uses the empirical acceleration attenuation law in the Taiwan area to derive the probability density distribution function (PDF) and the statistics for the earthquake-induced cyclic shear stress ratio (CSR). The PDF and the statistics for the cyclic resistance ratio (CRR) can be deduced from some probabilistic cyclic resistance curves. These curves are produced by the regression of the liquefaction and non-liquefaction data from the Chi-Chi earthquake and others around the world, using, with minor modifications, the logistic model proposed by Liao [J. Geotech. Eng. 114 (1988) 389]. The CSR and CRR statistics are used in conjunction with the first order and second moment method, to calculate the relation between the liquefaction probability, the safety factor and the reliability index. Based on the proposed method, the liquefaction probability related to a safety factor can be easily calculated. The influence of some of the soil parameters on the liquefaction probability can be quantitatively evaluated.     

Chlorinated volatile organic compounds found near the water surface of heavily polluted rivers

The objectives of this study were to identify the chlorinated volatile organic compounds near the water surface of two heavily polluted rivers in the south of Taiwan and compare their concentration distributions. Air samples were collected seasonally at the upstream, midstream and downstream water surfaces of each river and the chlorinated volatile organic compounds were analyzed qualitatively and quantitatively by gas chromatography and electron capture detector. Totally, twelve kinds of chlorinated volatile organic compounds were found at the water surfaces of both rivers and many of them were reported to be carcinogenic or probably carcinogenic to human. The results showed that each chlorinated volatile organic compound had its own distribution pattern and no good correlation of chlorinated volatile organic compounds between both rivers was obtained. The chlorinated volatile organic compounds identified at the river water surface of Fong Shan Stream showed much higher concentration than those of Chuen-Tsen River. Several chlorinated volatile organic compounds, including chlorodibromomethane, hexachlorobutadiene, 1,1,2,2-tetrachloroethene and 1,2-dibromo-3-chloropropane were found with much higher concentration (mean concentrations of 124.5 μg/m³, 334.5 μg/m³, 92.2 μg/m³, 268.4 μg/m³, respectively) at the water surface of Fong Shan Stream in some seasons (especially spring and summer, summer and winter, spring and winter, spring and summer, respectively) and they were reported to be possibly carcinogenic to human. Therefore, it may be concluded that the people living close to Fong Shan Stream possibly had higher health risks due to the release of volatile organic compounds from the heavily polluted river.     

Simplified-robust geotechnical design of soldier pile–anchor tieback shoring system for deep excavation

The shoring system that consists of soldier piles and anchor tiebacks is often used in deep excavations in sandy deposits. However, uncertainties often exist in the design of such shoring systems. In this article, a simplified-robust geotechnical design method is proposed to account for these uncertainties in the shoring system design. Specifically, for a given deep excavation, uncertain soil parameters and surcharges are treated as noise factors, and the parameters of soldier piles and tieback anchors are treated as design parameters. Robust design is then implemented as a multiobjective optimization problem, in which the design robustness is sought along with cost efficiency and safety requirements. A trade-off between design robustness and cost efficiency exists and the optimization usually leads to a Pareto front. By applying the knee point concept, the most preferred design that meets the safety requirements and yields the best compromise between design robustness and cost efficiency can be identified on the Pareto front. Improvements made to the existing robust geotechnical design method include an efficient formulation of the design robustness and a new procedure for finding the most preferred design in the design pool. The new simplified-robust geotechnical design method is illustrated with a real-world excavation case study.