土石坝的动态反应：离心机模型试验与数值模拟

为评估LIQCA程序是否能合理分析台湾仁义潭土石坝在地震时的反应,进行3个土石坝离心机模型试验,并对相同的土石坝与振动历时进行LIQCA动态数值分析。通过动态数值分析与离心机模型试验结果,探讨土石坝受震时超孔隙水压力的激增以及土体加速度在坝体不同填土区的变化,并评估LIQCA程序耦合在仿真土石坝受震时的可靠性。     

Performance of simple cross-interleaved Reed-Solomon decoding strategies for compact disc players

The complexity and performance of three simple error detection and correction strategies frequently used for the decoding of the cross-interleaved Reed-Solomon codes in digital compact disc ( CD) are compared. It is assumed that the number of byte errors in the input codeword is always a multiple of l a positive integer. By varying l from 1 to 32, the random to burst error performance of the various strategies is obtained. Specifically, it is shown that unless random errors are the main cause of concern, the best strategies seem to be those using erasure corrections. The results presented will be useful for deciding the decoding strategies to be adopted for CD players as well as in potential applications such as optical mass storage devices using the CD format     

Computer Techniques to Analyze Shell-and-Tube Heat Exchangers

This paper outlines computer analyses to predict thermal-hydraulics, flow-induced vibration, and fretting-wear damage in shell-and-tube heat exchangers. The analytical techniques are briefly described and the results arc illustrated by example. It is concluded that computer techniques can do much to improve the reliability and performance of heat exchangers.     

Long‐term (37 years) impacts of low‐head dams on freshwater shrimp habitat connectivity in northeastern Puerto Rico

Freshwater migratory shrimp in Puerto Rico depend on watershed connectivity, from stream headwaters to the ocean, to complete their life cycle. Moreover, shrimp populations in different watersheds are known to be connected in an island‐wide metapopulation. However, low‐head dams paired with water intakes on streams draining the El Yunque National Forest (EYNF) reduce streamflow. Here, we examine the cumulative effects of low‐head dams on shrimp habitat connectivity over 37 years across seven EYNF watersheds. We calculate total and refugia habitat connectivity (where refugia habitat is defined as predator‐free upstream reaches above waterfalls >5 m in height) at a monthly time step using a habitat‐weighted index of longitudinal riverine connectivity, which incorporates location and operation of water intakes and streamflow variability. Findings indicate total and refugia habitat connectivity declined over 37 years (by 27% and 16%, respectively) as additional water intakes have been placed in lower reaches of watersheds. On a monthly time step, the proportion of streamflow withdrawn has the largest effect on habitat connectivity, with the result that connectivity is ~17% lower during drought years than in nondrought years and ~7% lower in dry compared with wet seasons. Our analysis of this long‐term dataset highlights how cumulative effects of low‐head dams paired with water intakes have reduced shrimp habitat connectivity. These results underscore the importance of reducing existing withdrawal rates in EYNF, and locating intakes where effects on connectivity are minimal, if conserving shrimp habitat is a management objective.     

Successful wastewater reuse scheme and sustainable development: a case study in Adelaide

Freshwater availability to meet the growing needs of humankind has raised serious concerns in the recent past. Two immediate responses to counter this challenge are efficient allocation of the scarce resources, and development and use of alternative sources of water. While ‘water markets’ are seen as a means to achieve efficient allocation of the scare resources, treated wastewater and low‐quality water are now considered as potential sources of water to supplement the freshwater supplies. However, the latter option, that is use of reclaimed water as an alternative, imposes concerns regarding its suitability to sustain development. This is because of various issues related to wastewater usage and application. At the same time, it is also true that a successful and well‐planned reuse scheme can help achieve sustainability as evidenced in some isolated cases around the world. In line with this, the current paper adopts a case‐study approach to demonstrate how a successful reuse scheme in Adelaide, South Australia, has contributed to the sustainable development of the region. The paper looks into the socio‐economic and environmental dimensions of sustainability and arrives at a conclusion that properly planned and managed reuse schemes backed with effective regulatory and policy measures can lead to sustainable development.     

Removal of nickel from effluents by chelating ion exchange

BACKGROUND: Nickel is a highly toxic metal which is discharged into receiving waters by several industries, in particular, electroplating, PCB and electronics manufacturers. In the present study, a new ion exchanger has been assessed for its ability to remove nickel from solution. RESULTS: By comparing the SSE of different models in the nickel metal ion system, it seems that Redlich‐Peterson isotherm was the best fit model for the three metal ions. But the Langmuir was of a very similar magnitude. The equilibrium sorption capacity has been determined as 2.18 mmol/g and the batch contact time studies have been analyzed and compared using three kinetic models. The rate data were best correlated using the Elovich kinetic model. CONCLUSION: The batch sorption system is a well developed system for the application in the field of water pollution collected in small scale plants. The suitability of a sorbent is determined by the cost, sorption performance and regeneration efficiency. The sorption capacity of resin for nickel metal ions was determined as 2.18 mmol/g. In order to develop a treatment system design it is also important to determine the best kinetic model, Elovich kinetic model, to describe the rate of nickel removal. Copyright © 2008 Society of Chemical Industry     

The history of science and medicine in the context of COVID-19

This spotlight issue encourages reflection on the current COVID-19 pandemic, not simply through comparisons with previous epidemics, but also by illustrating that epidemics deserve study within their broader cultural, political, scientific, and geographic contexts. Epidemics are not solely a function of pathogens; they are also a function of how society is structured, how political power is wielded in the name of public health, how quantitative data is collected, how diseases are categorised and modelled, and how histories of disease are narrated. Each of these activities has its own history. As historians of science and medicine have long pointed out, even the most basic methodologies that underpin scientific research—observation, trust in numbers, the use of models, even the experimental method itself—have a history. They should not be taken as a given, but understood as processes, or even strategies, that were negotiated, argued for and against, and developed within particular historical contexts and explanatory schemes. Knowing the history of something—whether of numbers, narratives, or disease—enables us to see a broader range of trajectories available to us. These varied histories also remind us that we are currently in the midst of a chaotic drama of uncertainty, within our own unstable and unfolding narrative.     

Probabilistic model building in genetic programming: a critical review

Probabilistic model-building algorithms (PMBA), a subset of evolutionary algorithms, have been successful in solving complex problems, in addition providing analytical information about the distribution of fit individuals. Most PMBA work has concentrated on the string representation used in typical genetic algorithms. A smaller body of work has aimed to apply the useful concepts of PMBA to genetic programming (GP), mostly concentrating on tree representation. Unfortunately, the latter research has been sporadically carried out, and reported in several different research streams, limiting substantial communication and discussion. In this paper, we aim to provide a critical review of previous applications of PMBA and related methods in GP research, to facilitate more vital communication. We illustrate the current state of research in applying PMBA to GP, noting important perspectives. We use these to categorise practical PMBA models for GP, and describe the main varieties on this basis.     

Electrochemical oxidation of some basic alcohols on multiwalled carbon nanotube–platinum composites

Some composites of multiwalled carbon nanotubes, which were chemically treated in acidic and/or hydrogen peroxide solution, and platinum nanoparticles were prepared by the simple reduction in glycerol solution. Carboxylated and/or hydroxyl MWNTs were structurally analysed using X-ray photoelectron spectroscopy. In addition, the MWNT?CPt composites were characterized by XRD and TEM in detail. The electrochemical oxidation of some basic alcohols, which was catalyzed by the MWNT?CPt composites, was analysed by cyclic voltammetry. Their catalytic activities were studied with cyclic voltammograms of alcohols.