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81.
Computer Supported Cooperative Work (CSCW) - This paper places observational studies of women’s work in historical perspective. We present some of the very early studies (carried out in the... 相似文献
82.
Elizabeth J. Malloy Donna Spiegelman Ellen A. Eisen 《Computational statistics & data analysis》2009,53(7):2605-2616
This article presents an application and a simulation study of model fit criteria for selecting the optimal degree of smoothness for penalized splines in Cox models. The criteria considered were the Akaike information criterion, the corrected AIC, two formulations of the Bayesian information criterion, and a generalized cross-validation method. The estimated curves selected by the five methods were compared to each other in a study of rectal cancer mortality in autoworkers. In the stimulation study, we estimated the fit of the penalized spline models in six exposure-response scenarios, using the five model fit criteria. The methods were compared on the basis of a mean squared error score and the power and size of hypothesis tests for any effect and for detecting nonlinearity. All comparisons were made across a range in the total sample size and number of cases. 相似文献
83.
The influence of Arnheim's work on the author's research began with an experiment on the perception of visual balance. Two later research projects emerged from the profound influence of Arnheim's stance toward creation in the visual arts as a serious, cognitive endeavor. A series of meta-analyses were first conducted to test the claim that learning in the arts transfers to nonarts cognitive domains, but little evidence was found. Past research on the transfer hypothesis was found to be lacking because of its failure to assess learning in the parent domain. Therefore, a new research project was carried out to identify kinds of learning in the parent domain of visual arts. We identified eight thinking dispositions developed in serious visual arts classes, setting the stage for more plausible transfer studies. This study demonstrates that the visual arts inculcate basic skills in perception and cognition that exist both in the arts and sciences. All of the skills the authors describe can, with some modification, be transferred to the science laboratory. As Rudolf Arnheim has taught us, visual thinking is everywhere. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
84.
Optimization of Geoscience Laser Altimeter System waveform metrics to support vegetation measurements 总被引:1,自引:0,他引:1
The Geoscience Laser Altimeter System (GLAS) has collected over 250 million measurements of vegetation height over forests globally. Accurate vegetation heights can be determined using waveform metrics that include vertical extent and extent of the waveform's trailing and leading edges. All three indices are highly dependent upon the signal strength, background noise and signal-to-noise ratio of the waveform, as the background noise contribution to the waveforms has to be removed before their calculation. Over the last six years, GLAS has collected data during thirteen observation periods using illumination from three different lasers. The power levels of these lasers have changed over time, resulting in variable signal power and noise characteristics. Atmospheric conditions vary continuously, also influencing signal power and noise.To minimize these effects, we optimized a noise coefficient which could be constant or vary according to observation period or noise metric. This parameter is used with the mean and standard deviation of the background noise to determine a noise level threshold that is removed from each waveform. An optimization analysis was used with a global dataset of waveforms that are near-coincident with waveforms from other observation periods; the goal of the optimization was to minimize the difference in vertical extent between spatially overlapping GLAS observations. Optimizations based on absolute difference in height led to situations in which the total extent was minimized as well; further optimizations reduced a normalized difference in height extent. The simplest optimizations were based on a constant value to be applied to all observations; noise coefficients of 2.7, 3.2, 3.4 and 4.0 were determined for datasets consisting of global forests, global vegetation, forest in the legal Amazon basin and boreal forests respectively. Optimizations based on the power level or the signal-to-noise ratio of waveforms best minimized differences in waveform extent, decreasing the percent root mean squared height difference by 25-54% over the constant value approach. Further development of methods to ensure temporal consistency of waveform indices will be necessary to support long-term satellite lidar missions and will result in more accurate and precise estimates of canopy height. 相似文献
85.
This study aimed to gain insight into the interplay between citizens’ reactions on Twitter and governmental communications as well as their effects on self‐reliant behaviour and trust. Two experimental studies were conducted. In Study 1, participants first received other citizens’ reactions followed by the government's communications about how to act. Participants received supporting, opposing, mixed, or no reactions from other citizens. In Study 2, participants first received the government's communications with either certain or uncertain crisis information, followed by the different citizens’ reactions. The results showed that citizens’ reactions via Twitter are not necessarily detrimental to the effectiveness of governmental communications regarding self‐reliant behaviour. In addition, our findings suggest being careful with providing uncertain governmental communications during a crisis. 相似文献
86.
Long-lived renaming allows processes to repeatedly get distinct names from a small name space and release these names. This
paper presents two long-lived renaming algorithms in which the name a process gets is bounded above by the number of processes
currently occupying a name or performing one of these operations. The first algorithm is asynchronous, uses LL/SC objects, and has step complexity that is linear in the number of processes, c, currently getting or releasing a name. The second is synchronous, uses registers and counters, and has step complexity that
is polylogarithmic in c. Both tolerate any number of process crashes. 相似文献
87.
Computer self-efficacy (CSE) is known to enhance individual competence and performance in learning and using technology as well as improve technology attitudes and beliefs. Using longitudinal studies, CSE increases over time during organizational technology training. While these studies have been instrumental in our understanding of how self-efficacy operates in organizations, some critical questions remain unanswered. In particular these studies cannot answer how long it takes for one’s CSE to increase during training, nor can it describe the shape of the change trajectory (linear? some other shape?). The answers to these questions will provide organizations a much clearer perspective on training expectations, understanding when benefits from training through enhanced CSE might be expected, and when to start and ramp up/down training efforts. This study examines these issues by collecting repeated waves of data from 230 respondents in a technology lab training setting and using a relatively new structural equation modeling technique, latent growth modeling. Findings suggest that it takes about 2 months of training for individuals to display significant increases in CSE, and that the growth trajectory for CSE in non-linear. In the proposed model, anxiety is a significant predictor of CSE change, while CSE change significantly predicted software-specific self-efficacies. 相似文献
88.
This study investigated the impact of different modes of scaffolding on students who are learning science through a web-based collaborative inquiry project in authentic classroom settings and explored the interaction effects with students’ characteristics. The intervention study aimed to improve domain-specific knowledge and metacognitive awareness during online information problem solving (IPS) as part of an online inquiry project. Three experimental conditions (teacher-enhanced scaffolding, technology-enhanced scaffolding, and both forms of scaffolding) were compared with a control condition in a two-by-two factorial quasi-experimental design. Moreover, gender and prior knowledge were examined as two factors which may have a significant impact on Web-based learning. In a four-week field study in secondary science education, pretest-posttest differences were measured. In total 347 students from 18 secondary school classes were involved and the classes were randomly distributed over the 4 conditions. Our findings support the notion of multiple scaffolding as an approach to enhance both knowledge acquisition and metacognitive awareness with respect to IPS-processes and to meet a mix of students with different needs within the context of a web-based inquiry learning project. 相似文献
89.
Faith Ellen Panagiota Fatourou Eleftherios Kosmas Alessia Milani Corentin Travers 《Distributed Computing》2016,29(4):251-277
A universal construction is a general mechanism for obtaining a concurrent implementation of an object from its sequential code. We show that there is no universal construction that is both disjoint-access parallel (guaranteeing the processes operating on different parts of an implemented object do not interfere with one another) and wait-free (guaranteeing progress for each nonfaulty process when accessing an object). In contrast, we present a universal construction which results in disjoint-access parallel, wait-free implementations of any object provided there is a bound on the number of data items accessed by each operation supported by the object. 相似文献
90.
We give matching upper and lower bounds of \(\varTheta(\min(\frac{\log m}{\log \log m},\, n))\) for the individual step complexity of a wait-free m-valued adopt-commit object implemented using multi-writer registers for n anonymous processes. While the upper bound is deterministic, the lower bound holds for randomized adopt-commit objects as well. Our results are based on showing that adopt-commit objects are equivalent, up to small additive constants, to a simpler class of objects that we call conflict detectors. Our anonymous lower bound also applies to the individual step complexity of m-valued wait-free anonymous consensus, even for randomized algorithms with global coins against an oblivious adversary. The upper bound can be used to slightly improve the cost of randomized consensus against an oblivious adversary. For deterministic non-anonymous implementations of adopt-commit objects, we show a lower bound of \(\varOmega(\min(\frac{\log m}{\log \log m}, \frac{\sqrt{\log n}}{\log \log n}))\) and an upper bound of \(O(\min(\frac{\log m}{\log \log m},\, \log n))\) on the worst-case individual step complexity. For randomized non-anonymous implementations, we show that any execution contains at least one process whose steps exceed the deterministic lower bound. 相似文献