Frequency dependent dynamic properties from resonant column and cyclic triaxial tests

The resonant column (RC) and cyclic triaxial (CT) devices are commonly used for the measurement of soils’ dynamic properties. The results of these tests do not agree when extrapolated to similar strain levels. The main objectives of this paper are to evaluate the effect of excitation frequency on the dynamic properties of soils, and to provide a methodology to reconcile shear modulus values obtained from RC and CT tests. The effect of frequency on the dynamic properties is evaluated using the new non-resonance (NR) method in the RC device and CT tests. Sand specimens with varying percentages of bentonite-water mixture and a clay specimen are tested. The results obtained from RC tests utilizing the NR method indicate significant change in shear modulus with frequency. The extrapolation of shear modulus from the conventional RC results to shear strains used in CT is significantly overestimated. The extrapolations improved when the results were corrected for frequency effect inferred from the NR method.     

Analysis of adaptive detection of moderately fluctuating radar targets in target multiplicity environments

In this article, we provide a complete detection analysis, in its exact form, of what is known as moderately fluctuating radar targets when the background environment contains a number of interfering targets along with the target under test. The illumination of this class of radar targets by a coherent pulse train, return a train of correlated pulses with a correlation coefficient in the range 0<ρ<1 (intermediate between SWII and SWI models). Since the adaptive detection is one of the desirable features for modern radar receivers, it becomes of importance to adaptively detect this class of targets. The attractive class of adaptive detectors is that based on order-statistics (OS) technique. The more advanced version of the OS algorithm, known as the generalized trimmed-mean (GTM) scheme, is chosen here to carry out this task. It implements trimmed averaging of a weighted ordered range samples. This processor is analyzed for the case where the radar receiver incorporates a postdetection integrator amongst its contents and where the operating environment is multitarget. The primary and the secondary interfering targets are assumed to be fluctuating in accordance with partially correlated χ² fluctuation model. SWI and SWII well-known models represent the cases where the signal is completely correlated and completely decorrelated, respectively, from pulse to pulse. It is shown that the processor performance improves, for weak SNR of the primary target, as the correlation coefficient ρ_s increases and this occurs either in the absence or in the presence of spurious targets. For strong SNR, on the other hand, the processor performance degrades as ρ_s increases and the SWI and SWII models enclose the correlated target case and this behavior is common for all GTM based schemes.     

Fragments of your communication: Email,vmail, and fax

Abstract

How are new media, such as electronic mail, voice mail, and fax, used when people have access to several of them simultaneously? This paper reports findings from a field study of media use in four sizable subunits within two large organizations where most employees had access to email, vmail, and fax. Respondents tended to use multiple electronic media rather than relying on one. However, they also showed a tendency to prefer one medium for asynchronous communication and to use the others for occasional, specialized purposes. Further, there were considerable differences across subunits in typical media use patterns. Although respondents expressed strong desires for multimedia integration, this study suggests that technological integration may not necessarily result in seamless, collaborative work.     

Evaluating university performance using reference point based composite indicators

In this paper, we propose the application of a novel methodology to build composite indicators, in order to evaluate university performance. We analyse separately the three basic dimensions of our university system (research, teaching and technology transfer), because we are interested in getting a more accurate vision of each of them. In order to build the composite indicators, we use a multi-criteria analysis technique, based on the double reference point method. One advantage of this technique is the possibility to use reference levels, in such a way that the results obtained are easily interpreted in terms of the performance of the university with respect to these levels. Besides, aggregations for different compensation degrees are provided. In order to illustrate the advantages of this method, it has been applied to evaluate the performance of the public universities of the Spanish region of Andalucía, for year 2008. The results show that the performance of the Andalusian public universities in the teaching block is better than in the research and technology transfer blocks. The application lets us conclude that the methodology offers a warning system to assist in strategic decision making, and the values of the indicators allow us to find fields of improvement in all areas.     

Language effects in international testing: the case of PISA 2006 science items

We investigate the extent to which language versions (English, French and Arabic) of the same science test are comparable in terms of item difficulty and demands. We argue that language is an inextricable part of the scientific literacy construct, be it intended or not by the examiner. This argument has considerable implications on methodologies used to address the equivalence of multiple language versions of the same assessment, including in the context of international assessment where cross-cultural fairness is a concern. We also argue that none of the available statistical or qualitative techniques are capable of teasing out the language variable and neutralising its potential effects on item difficulty and demands. Exploring the use of automated text analysis tools at the quality control stage may be successful in addressing some of these challenges.     

The impact of technology on the enactment of “inquiry” in a technology enthusiast's sixth grade science classroom

This study investigated the impact of the use of computer technology on the enactment of “inquiry” in a sixth grade science classroom. Participants were 42 students (38% female) enrolled in two sections of the classroom and taught by a technology‐enthusiast instructor. Data were collected over the course of 4 months during which several “inquiry” activities were completed, some of which were supported with the use of technology. Non‐participant observation, classroom videotaping, and semi‐structured and critical‐incident interviews were used to collect data. The results indicated that the technology in use worked to restrict rather than promote “inquiry” in the participant classroom. In the presence of computers, group activities became more structured with a focus on sharing tasks and accounting for individual responsibility, and less time was dedicated to group discourse with a marked decrease in critical, meaning‐making discourse. The views and beliefs of teachers and students in relation to their specific contexts moderate the potential of technology in supporting inquiry teaching and learning and should be factored both in teacher training and attempts to integrate technology in science teaching. © 2006 Wiley Periodicals, Inc. J Res Sci Teach