Regional daily baseflow prediction

The purposes of this study are to identify the bias of applying the analysis of a log–log plot of baseflow and to derive an equation to describe successive regional mean baseflow. The function ?dQ/dt = a Q^b has been used to describe baseflow in many studies that obtain the values of a and b from the log–log plot. According to analysis in this study, the value of 1 can be assigned to b in two boundary conditions, but the parameter a is proved to be related to the depth of water table and starting time of recession and thus different values of a may be found for different recession events. This paper points out that no single regression line can be obtained by plotting all baseflow data on a log–log diagram. Instead, there should be parallel lines, and each for a recession event. It implies that no single set of parameters a and b can be applied to predict baseflow. Thus, a new equation describing the relationship between three successive mean baseflows was derived in this study. The bias in the analysis of the log–log plot and the ability of the derived equation to predict baseflow were verified for five watersheds in Taiwan. Results indicate that the formula of mean baseflow prediction can provide reasonable estimates of flows with a leading time of 6 days. Furthermore, stream flows of the Tonkawa creek watershed in USA were used to verify that using average flows can result in better predictions than using instantaneous flows. Copyright © 2004 John Wiley & Sons, Ltd.     

Using multiple‐variable indicator kriging to assess groundwater quality for irrigation in the aquifers of the Choushui River alluvial fan

This work attempted to locate clean and safe groundwater for irrigation use in the Choushui River alluvial fan. Multiple‐variable indicator kriging (MVIK) was adopted to evaluate numerous hydrochemical parameters for a standard of water quality for irrigation in Taiwan. Many hydrochemical parameters in groundwater were distinguished into three main categories—salinity/sodium hazard, nitrogen hazard and heavy metal hazard. Safe and potential hazardous regions of groundwater for irrigation were delineated according to different probabilities estimated by MVIK. The probabilistic results of the classifications gave an opportunity to explore the spatial uncertainty of the hazards and helped government administrators establish a sound policy associated with the development and management of groundwater resources. Analysis of the results indicate that the central distal‐fan and mid‐fan aquifers are the best places to extract clean and safe groundwater for irrigation, and the deep aquifer (exceeding 200 m depth) has wider regions with clean and safe groundwater for irrigation than shallow aquifers. The northern and southern aquifers, with multiple hazards, limit groundwater use for irrigation. Although the proximal‐fan aquifer is a zone of groundwater recharge, the high nitrogen content seriously affects the environment and is not suitable for irrigation use. Copyright © 2008 John Wiley & Sons, Ltd.     

Global distribution of thermospheric heat sources: EUV absorption and joule dissipation

The global distribution and temporal variations of thermospheric heating due to Joule dissipation of measured ionospheric electric fields are computed. It is shown that the volume Joule dissipation rate at high and middle latitude is similar in magnitude and altitudinal profile to the global solar EUV absorption rate discussed in the previous papers. Thus, Joule dissipation contributes significantly towards reconciling the quantitatively known sources of thermospheric heat input and that required to maintain the normal thermosphere. The combined heat source due to EUV absorption and Joule dissipation varies with the annual cycle in a manner closely resembling that of the thermospheric density.     

Initial moduli of particulated mass with frictional contacts

The stiffness characteristics of a packing of granules are influenced by the particle interactions at contacts, the void ratio, the co-ordination number and the packing structure. A stress-strain relationship for the packings of spheres is presented. The relationship explicitly includes the contact force-displacement law and the parameters characterizing the packing structure. The initial moduli computed using this relationship are compared with experimental measurements and empirical equations for sands. The theoretical results are also compared with experimental results on packings of glass balls. Closed-form solutions are derived for statistically isotropic packings under initial isotropic stress conditions. Numerical solutions for the stiffness properties are obtained for anisotropic initial stress conditions and anisotropic packing structures.     

Atmospheric density from the low altitude satellite 1970-48A: Comparison of orbital decay measurements,accelerometer measurements and atmospheric models

Atmospheric densities have been deduced from high resolution radar-determined orbital decay data and from data obtained from a uniaxial accelerometer flown onboard the low altitude satellite 1970-48A. Data were obtained during late June and early July, 1970. The orbital decay-deduced densities, having an effective 6 hr temporal resolution, were determined at an altitude of 143 km, essentially one-half scale height above perigee. The accelerometer deduced densities at the same altitude were obtained on both the approaching-perigee and leaving-perigee portions of each of fifty-nine orbits. A detailed comparison of the densities derived from both types of data is presented. In general, agreement is very good. A comparison of both types of data has also been made with the Jacchia 1970 and 1971 atmospheric models as well as the new OGO-6 atmospheric model. The Jacchia models display reasonable agreement with the data, but the OGO-6 model is unsuitable as a representation of atmospheric density at this altitude.     

Cyclical Events in the Life and Death of an Ephemeral Polychaete Reef on a Tropical Mudflat

The polychaete (sabellariid-spionid) reefs at Jeram shore (Malaysia) grow up on soft-bottom mudflats and appear short-lived. It is postulated that such reef building results from the succession of polychaete species in response to the changing environment modulated by the extreme hydrometeorological events. To elucidate the biological succession of the reef cycle in relation to the environment, two reef patches on the intertidal mudflat were studied, both spatially (horizontal and vertical community structure) and temporally (June 2012 to January 2014). The Jeram polychaete reef cycles through four phases within a year: pre-settlement phase (March–May), growth phase comprising primary (May–November) and secondary (October–January) successional stages, stagnation phase (December–January), and destruction phase (January–March). The reef dynamics appear to be linked to the regional monsoon climate and local hydrological conditions. At the onset of the southwest monsoon (May), strong erosive forces initiate the reef’s primary succession of the growth phase where the dominant polychaete Sabellaria jeramae colonize and rapidly grow on the exposed lag deposits of shells. During the northeast monsoon (November–March), stronger depositional forces cover the developed reef with fine sediments that are colonized by another polychaete, the spionid Polydora cavitensis during the reef’s secondary succession of the growth phase. On the muddy substrate surrounding the reef clumps, mudflat polychaetes were the most abundant macrobenthos followed by anomurans, gastropods, carideans, and brachyurans. However, these mudflat macrobenthos play no obvious or direct role in initiating the growth of the reef which is likely the result of settlement of dispersed polychaete larvae from unknown offshore reefs. On the other hand, the reef presence has a positive effect on the presence or abundance of surrounding mudflat macrobenthos such as mudflat polychaetes, shrimps, crabs, and gastropods.     

A full-scale field study for performance evaluation of axially loaded large-diameter cylinder piles with pipe piles and PSC piles

This paper presents the results from a pile load testing program for a bridge construction project in Louisiana. The testing includes two 54-in. open-ended spun cast concrete cylinder piles, one 30-in. open-ended steel pile and two (30- and 16-in.) square prestressed concrete (PSC) piles driven at two locations with very similar soil conditions. Both cone penetration tests (CPTs) and soil borings/laboratory testing were used to characterize the subsurface soil conditions. All the test piles were instrumented with vibrating wire strain gauges to measure the load distribution along the length of the test piles and measure the skin friction and end-bearing capacity, separately. Dynamic load tests were performed on all test piles at different times after pile installations to quantify the amount of setup with time. Static load tests were also performed on the PSC and open-ended steel piles. Due to expected large pile capacities, the statnamic test method was used on the two open-ended cylinder piles. The pile capacities of these piles were evaluated using various CPT methods (such as Schmertmann, De Ruiter and Beringen, LCPC, Lehane et al. methods). The result showed that all the methods can estimate the skin friction with good accuracy, but not the end-bearing capacity. The normalized cumulative blow counts during pile installation showed that the blow count was always higher for the PSC piles compared to the large-diameter open-ended cylinder pile, regardless of pile size and hammer size. Setup was observed for all the piles, which was mainly attributed to increase in skin frictions. The setup parameters “A” were back-calculated for all the test piles and the values were between 0.31 and 0.41.     

Performance evaluation of steel reduced flange plate moment connections

This study details a new moment connection that overcomes difficulties in achieving field‐weld quality and eliminates steel beam buckling encountered in steel moment connections. This study presents cyclic test and finite element analysis results of full‐scale subassemblies using steel reduced flange plates (RFPs) to connect steel beam flanges and the column without any other direct connection. Since the RFP connection is designed as strong column‐strong beam‐weak RFPs, the RFP functions as a structural fuse that eliminates weld fractures and beam buckling. Test and analytical results show that (1) the connections transferred the entire beam flexural strength to the column and reached an interstorey drift of 4% with minor strength degradation, (2) failure of the connections was owing to buckling or fracturing of the RFP and not of the beam, and (3) the RFP connection subassembly, modelled using the nonlinear finite element computer program ABAQUS, exhibited hysteretic behaviour similar to that of the flange plate (FP) moment connection subassembly. The inelastic buckling force of the RFP was also evaluated by nonlinear regression analyses performed on a nonlinear model that relates buckling force to RFP geometries. Copyright © 2007 John Wiley & Sons, Ltd.     

Tracking rapidly changing dynamical systems using a non‐parametric statistical method based on wavelets

A non‐parametric statistical method of tracking rapidly changing dynamical systems is introduced. The method implements the non‐linear wavelet thresholding estimator to estimate the evolutionary transfer function of the system. The consistency and optimality of the resulting estimate of our method on rapidly changing systems are stated, while no linear estimator can achieve the same optimality. Two examples of real data are studied using this non‐parametric method, including two vertical seismic array case studies and a series of seismic slope experiments. The analysis results are consistent with previous research for the vertical seismic array data. Moreover, our estimate is superior to those from previous research in the sense that our estimate is neither over‐smoothed nor under‐smoothed. The ana‐ lysis results are also consistent with the experimental observations for the seismic slope experimental data. Copyright © 2003 John Wiley & Sons, Ltd.