共查询到20条相似文献,搜索用时 15 毫秒
1.
Ellen De Pauw Stijn Daniels Tom Brijs Elke Hermans Geert Wets 《Accident; analysis and prevention》2014
The present study evaluates the speed effects of fixed speed cameras on motorways. Two locations with speed cameras were extensively examined in a quasi-experiment: (1) a two-lane motorway and (2) a three-lane motorway, each with a posted speed limit of 120 km/h and sited in Flanders, Belgium. The effect is analysed through a before-and-after comparison of travel speeds. General time trends and fluctuations were controlled through the analysis of the speeds at comparison locations. At each of the two roads, data were gathered at five measurement points from 3 km upstream to 3.8 km downstream of the camera. Three outcomes were analysed: (1) average speed, (2) the odds of drivers exceeding the speed limit and (3) the odds of drivers exceeding the speed limit by more than 10%. Speeds decreased on average by 6.4 km/h at the camera locations. Both the odds of drivers exceeding the speed limit (−80%) and the odds of drivers exceeding the speed limit by more than 10% (−86%) decreased considerably. However, before and beyond the cameras the speeds hardly, if at all, reduced. Moreover, the analyses of the speed profiles before and beyond the cameras show that drivers do slow down quite abruptly before the camera and speed up again after passing the camera. It is concluded that a V-profile is found in the spatial speed distribution for both locations. 相似文献
2.
Peter Ralston 《国际生产研究杂志》2020,58(16):5006-5019
The purpose of this research is to develop a better understanding of smart systems and autonomous processes of the Industry 4.0 era. Does the implementation of Industry 4.0 processes and systems expose firms to higher levels of risk in the supply chain through capability loss or does Industry 4.0 spur capability enhancement and thereby increase supply chain resilience? Industry 4.0 is centred on the idea that certain tasks and decisions can be automated through smart systems and autonomous processes. However, is there a risk of losing critical capabilities and the ability to be flexible, agile and resilient to unexpected disruptions in the supply chain? In order to address these questions, this research presents results from semi-structured interviews across multiple industries to provide findings on firms’ uses of smart systems and capability development associated with these systems. Results from this exploratory study may be classified into two primary insights. First, although Industry 4.0 systems are new and, in many cases untested, firms are eager regarding the potential of smart systems to positively impact firm performance and to leverage Industry 4.0 processes for a competitive supply chain advantage. Second, companies did not claim any human capability loss associated with Industry 4.0. In fact, these smart systems may lead to increased supply chain resilience because of capability enhancement and new skill development. 相似文献
3.
Patents and relevant topics are gaining momentum in economic analysis and scientific research with the rapid global intellectual property filings growth. However, a corresponding increase seems to be unspectacular in patent research publications, especially under the category of information science and library science. This paper provided a retrospect to the existing studies on patents collected from web of science and emphatically characterized the current situation through performing a series of bibliometric analysis. Prominent authors and institutions from mainland China, Taiwan and Belgium have carried out various studies on patent separately or jointly. Topics involved in 884 journal papers are reclassified from perspectives of the development, application and analysis of patents based on the results of keyword co-occurrence and typical publications in each stage. The final, but the novel part of this study was a sentence-by-sentence analysis of conclusive and citing ideas of recent publications, for tracing problems and potential researchable topics and indicating that patent research still has more spaces to move up. 相似文献
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Given the burden of injury, economic, environmental and social consequences associated with speeding, reducing road traffic speed remains a major priority. Intelligent speed adaptation (ISA) is a promising but controversial new in-vehicle system that provides drivers with support on the speed-control task. In order to model potential system uptake, this paper explores drivers’ preferences for two different types of ISA given a number of alternative fiscal incentives and non-fiscal measures, using a stated preference approach. As would be expected with such a contentious issue, the analysis revealed the presence of significant variations in sensitivities and preferences in the sample. While a non-negligible part of the sample population has such strong opposition to ISA that no reasonable discounts or incentives would lead to them buying or accepting such a system, there is also a large part of the population that, if given the right incentives, would be willing or even keen to equip their vehicle with an ISA device. 相似文献
6.
Mundell CG 《Philosophical transactions. Series A, Mathematical, physical, and engineering sciences》2002,360(1801):2725-2740
Violent activity in the nuclei of galaxies has long been considered a curiosity in its own right; manifestations of this phenomenon include distant quasars in the early Universe and comparatively nearby Seyfert galaxies, both thought to be powered by the release of gravitational potential energy as material from the host galaxy accretes onto a central supermassive black hole (SMBH). Traditionally, the broader study of the formation, structure and evolution of galaxies has largely excluded active galactic nuclei. Recently, however, this situation has changed dramatically, both observationally and theoretically, with the realization that the growth and influence of the SMBH, the origin and development of galaxies and nuclear activity at different epochs in the Universe may be intimately related. The most spectacular fireworks seen in distant quasars may be relatively easy to explain, since the era of greatest quasar activity seems to coincide with turbulent dynamics at the epoch of galaxy formation in the young, gas-rich Universe. Ubiquitous black holes are believed to be a legacy of this violent birth. Alternatively, black holes may be the seeds that drive galaxy formation in the first place. Closer to home, and hence more recently in the history of the Universe, a fraction of comparatively ordinary galaxies, similar to our own, has reignited their central engines, albeit at a lower level of activity. Since these galaxies are more established than their younger and more distant counterparts, the activity here is all the more puzzling. Whatever the mechanisms involved, they are likely to play an important role in galaxy evolution. I review the intriguing evidence for causal links between SMBHs, nuclear activity and the formation and evolution of galaxies, and describe opportunities for testing these relationships using the next generation of earthbound and space-borne astronomical facilities. 相似文献
7.
The psychological digital divide (PDD) significantly impacts participation and may hinder the development of smart rural communities. This study aimed to address the issue by conducting a questionnaire survey of 394 elderly individuals from rural China, revealing the essential characteristics and core mechanisms of PDD based on the relative deprivation theory (RDT). The study also focused on a moderation test of cognitive age to validate its critical role in the formation of PDD among rural elderly individuals. The final results confirmed the stability of the PDD induction model and highlighted that the information systems (IS) continuance intention of the elderly can be affected by both technological and social environments, through relative digital deprivation. Specifically, social exclusion and technology anxiety were identified as key drivers of PDD, with technology anxiety having a stronger impact. Furthermore, the cognitive age of elderly individuals intensifies the negative influence of relative digital deprivation on IS continuance intention, while also strengthening the relationship between social exclusion and relative digital deprivation. These findings not only shed light on the nature of PDD but also provide a theoretical framework for understanding the transition from social to digital exclusion. 相似文献
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This paper compares R&D productivity change across countries considering the fact that national R&D expenditure may produce multiple outputs, including patents and journal articles. Based on the concept of directional distance function and Luenberger productivity index, this paper develops a Luenberger R&D productivity change (LRC) index and then decomposes it into R&D efficiency change (catch-up effect) and R&D technical change (innovation effect). Utilizing a panel dataset of 29 countries over the 1998–2005 period to implement the empirical estimation, the results show that the R&D productivity growth is mainly attributed to the innovation effect; meanwhile, non-OECD countries have better performance on both efficiency change and technical change than their OECD counterparts. Moreover, patent-oriented R&D productivity growth serves as the main source of national R&D productivity growth than the journal article-oriented one. 相似文献
10.
The thermal conductivity of hole-doped Cu-O plane high-T
c
perovskites exhibits a dramatic increase belowT
c
which results in a pronounced peak nearT
c
/2. The origin of this peak was initially thought to arise from an enhancement in the mean-free path of phonons as the charge carriers undergo condensation. Indeed, excellent fits to the data can be obtained with physically reasonable parameters using the conventional theory of lattice conduction in superconductors. In contrast, a recently observed sharp decrease in the quasiparticle scattering rate of YBCO single crystals belowT
c
has motivated proposals for an electronic origin of the thermal conductivity peak. We shall critically examine experimental evidence and highlight relative advantages and shortcomings of the two contrasting interpretations. Furthermore, we shall draw attention to recently available data on the relaxation time of out-of-equilibrium carriers in Cu-O superconductors obtained using pump-probe femtosecond laser studies and what new light they shed on the controversy. 相似文献
11.
John Hudson 《Scientometrics》2017,113(2):735-750
Different academic disciplines exhibit different styles, including styles in journal titles. Using data from the 2014 Research Excellence Framework (REF) in the UK we are able to identify the stylistic trends of different disciplines using 155,552 journal titles across all disciplines. Cluster analysis is then used to group the different disciplines together. The resulting identification fits the social sciences, the sciences and the arts and humanities reasonably well. Economics overall, fits best with philosophy, but the linkage is weak. When we divided economics into papers published in theory, econometrics and the remaining journals, the first two link with mathematics and computer science, particularly econometrics, and thence the sciences. The rest of economics then links with business and thence the social sciences. 相似文献
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This paper categorizes in terms of size, the behaviour of the Basque small and medium-sized enterprises (SMEs) in the use of information technology (IT) tools as enablers of knowledge management practices. As part of this research, this article concludes as well about the suitability of collaborative tools in organic and flexible less informal organizations, such as small enterprises. The evolution of technology trends towards the use of collaborative platforms to support knowledge capturing and sharing in a less standardized way. Therefore, this characteristic of collaborative tools allows the smallest SMEs to have at their disposal a flexible tool for knowledge sharing. 相似文献
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A three-dimensional numerical model of the down-flow fluidized bed (Downer) with a newly designed distributor was applied to investigate the particle distribution profiles using combined computational fluid dynamics (CFD) and the discrete element method (DEM). A realistic model of DEM, which calculates the contact force acting on the individual particles, is used to monitor the movement of individual particles in the bed. The contact force is calculated using the concepts of the spring, dash-pot, and friction slider. The flow field of gas is predicted by the Navier–Stokes equation. This CFD–DEM model provides information regarding the particle movement and distribution, the particle velocity, and the gas velocity in the bed under different air-particle mixture conditions. The results demonstrate that the air supply conditions directly influence the particle distribution uniformity. Furthermore, the numerical predictions for the axial and radial profiles of the particle distribution were found to agree well with the experimental results obtained by electrical capacitance tomography (ECT). 相似文献
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The phenomenon of “temperature dichotomy”, or anomalous heating of surface water under the ice up to temperatures exceeding 4 °C is known to take place occasionally in solar-heated ice-covered freshwater lakes and has usually been explained by the stabilizing effect of the weak vertical salinity gradient created by the melt water flux from the ice and supporting the unstable temperature distribution. Here, we report an observation of the local temperature maximum in the upper part of the water column of ice-covered Lake Vendyurskoe (northwestern Russia). The observation was accompanied by vertically resolved measurements of the conductivity allowing estimation of the dissolved salts effect on the vertical density distribution. The results demonstrate insufficiency of the salt gradient to support the vertical stability of water column. Therefore, we suggest the vertically inhomogeneous radiation absorption to be the probable stabilizing mechanism here, similarly to radiatively heated boundary layers in the ocean, the atmosphere and star interiors. An analytical solution of the heat transfer equation is derived describing the temperature profile evolution in ice-covered lakes subject to solar radiation heating above the maximum density temperature. Observed daytime temperature profiles agree well with the analytical model that suggests the absence of convective mixing. According to the model, the temperature maximum is formed within a day that supports the hypothesis about the stabilizing effect of the solar radiation absorption. We conclude that in temperate lakes the warm layer should have diurnal character and should be destroyed during the nighttime by convection. In polar lakes, in turn, the warm layer can exist during essentially longer periods that is supported by application of the model to the previously published data from Lake Peters, Alaska. In this case, the ice melting rate can be significantly affected by the increased temperature gradient beneath the ice. Apart from potential effects on the ice melting rate and the spring plankton development in lakes, the regime represents a rare geophysical example of instability driven solely by radiative heating with many useful analogies in planetary and stellar physics. 相似文献
17.
Scientometrics - To what extent has English become the dominant language of scientific communication? What factors push non-native speakers to publish their research in English rather than their... 相似文献
18.
Nicholas E. Cherolis Daniel J. Benac Wesley D. Pridemore 《Journal of Failure Analysis and Prevention》2016,16(5):828-841
This article discusses practical differences between high-cycle fatigue and low-cycle fatigue at relatively lower temperatures in rotating equipment and the equipment attached to it. Methods to identify the failure mode are discussed so proper prevention measures can be put in place to prevent future occurrences. Examples of typical components are provided to show the methods in action. 相似文献
19.
In many countries culture, practice or regulations inhibit the co-presence of relatives within the university faculty. We test the legitimacy of such attitudes and provisions, investigating the phenomenon of nepotism in Italy, a nation with high rates of favoritism. We compare the individual research performance of “children” who have “parents” in the same university against that of the “non-children” with the same academic rank and seniority, in the same field. The results show non-significant differences in performance. Analyses of career advancement show that children’s research performance is on average superior to that of their colleagues who did not advance. The study’s findings do not rule out the existence of nepotism, which has been actually recorded in a low percentage of cases, but do not prove either the most serious presumed consequences of nepotism, namely that relatives who are poor performers are getting ahead of non-relatives who are better performers. In light of these results, many attitudes and norms concerning parental ties in academia should be reconsidered. 相似文献
20.
Retracted publications are a crucial, yet overlooked, issue in the scientific community. The purpose of this study was to analyze the prevalence, characteristics and reasons of Malaysian retracted papers. The Web of Science and Scopus databases were queried to identify Malaysian retracted publications. Available versions of original articles and publication notices were accessed from journal websites. The publications were assessed for various characteristics, including reason for retraction, based on the Committee on Publication Ethics guidelines, and the authority calling for the retractions. From 2009 to June 2017, 125 Malaysian publications comprising (33 journal articles and 92 conference papers) were retracted. There was a spike in the prevalence of retracted articles in 2010 and 2012 with 42 articles (33.6%) and 41 articles (32.8%) respectively from the 125 retracted articles. The mean time from electronic publication to retraction was 1 year. There is no significant relationship between a journal quartile and the mean number of months to retraction (P = 0.842). The reason for retraction for conference papers was specified as “violation of publication principle”. Journal articles were retracted mainly for duplicate publication, plagiarism, compromised peer review process, and self-plagiarism. Most retracted articles do not contain flawed data; and only 2 retracted articles have been accused of scientific mistakes. The study concludes that retractions were mostly due to the authors misconduct. Despite the increases, the proportion of published scholarly literature affected by retraction remains very small, indicating that retraction represents an uncommon, yet potentially increasing and incipient, issue within Malaysian papers, which publishers as well as editors may have consistently and sufficiently addressed. 相似文献