预应力混凝土路面设计准则研究   总被引：2，自引：0，他引：2  

孙宝俊  Roger K.Hawkins  吕志涛 《东南大学学报》2000,16(1):80-88

对混凝土路面板施加预应力,可显著提高其承载能力,因而相同荷载下板厚可减小.预应力改变了路面板的结构形式,可抵抗更大的冲击、振动和超载.本文讨论了设计预应力混凝土路面的要点,提出了预测预应力路面早期、使用阶段及开裂后压应力的设计步骤.必须清楚区分反复荷载和非反复荷载中的变量,同样需要检查预应力路面在超载下开裂后的恢复情况.文末附一个设计实例说明该方法的应用.,With a concrete pavement slab prestressed, its load-carrying capacity can be significantly increased, thus a thinner slab may be used for the same loading. Prestressing modify the structural behavior of the pavement slab and there is a greater resistance to impact, vibration and overloading. This paper discusses the major design considerations necessary in the successful construction of prestressed concrete pavements and presents a design procedure developed to predict the compressive stress due to prestressing in the pavements at early stage, during service and after cracking. Variation in the approach for repetitive and nonrepetitive loads is clearly distinguished. Check on the recovery after cracking for overloading in prestressed pavements is also needed. Finally, a design example is illustrated the application of the approach developed.  相似文献   

Mapping the Final Frontier: A Publisher’s Experience Launching an Open Access Journal in the Burgeoning Mixed Access Economy     

James Butcher  Kevin Davies  Karen L. Hawkins  Sharon Dyas-Correia 《期刊图书馆员》2015,68(1-4):325-331

This article describes a program session that focused on publishers’ experiences launching Open Access (OA) journals and lessons learned. The speakers discussed the current journal marketplace, current journal business models, and the possible shape of the OA landscape and marketplace in the future.  相似文献   

Basic Serials Cataloging Workshop     

Les Hawkins  Hien Nguyen  Stephen Kharfen 《期刊图书馆员》2015,68(1-4):5-16

  相似文献   

An optically transparent membrane supports shear stress studies in a three-dimensional microfluidic neurovascular unit model     

Katelyn L. Sellgren  Brian T. Hawkins  Sonia Grego 《Biomicrofluidics》2015,9(6)

We report a microfluidic blood-brain barrier model that enables both physiological shear stress and optical transparency throughout the device. Brain endothelial cells grown in an optically transparent membrane-integrated microfluidic device were able to withstand physiological fluid shear stress using a hydrophilized polytetrafluoroethylene nanoporous membrane instead of the more commonly used polyester membrane. A functional three-dimensional microfluidic co-culture model of the neurovascular unit is presented that incorporates astrocytes in a 3D hydrogel and enables physiological shear stress on the membrane-supported endothelial cell layer.  相似文献   

Effects of stance width on performance and postural stability in national-standard pistol shooters     

Hawkins RN  Sefton JM 《Journal of sports sciences》2011,29(13):1381-1387

The aim of the present study was to determine whether changing stance width would result in a corresponding change in postural and/or pistol stability. Twelve national-standard male air pistol shooters performed 10 shots each at five stance widths (30 cm, 45 cm, 60 cm, 75 cm, and 90 cm). Postural stability was determined by measuring centre-of-pressure changes with a dual force-platform system. Shooting mechanics measures were determined by a NOPTEL ST-2000 optoelectronic training system. Medial-lateral centre-of-pressure excursion (F?,?? = 7.17, P < 0.001, effect size = 0.99) and speed (F?,?? = 77.03, P < 0.001, effect size = 3.88) were reduced as stance width decreased. Centre of gravity fine (the percentage of time held within an area the size of the ten-ring) improved during narrower stance widths (F?,?? = 12.49, P < 0.001, effect size = 0.71). Our findings suggest that stance width affects postural and pistol stability in national-standard air pistol athletes. Moreover, the current method of suggesting a wider stance to improve shooting performance should be reconsidered and perhaps air-pistol shooters should use a 30-cm stance width to improve postural stability and shooting performance.  相似文献   

Capillary flow in sacrificially etched nanochannels     

Hamblin MN  Hawkins AR  Murray D  Maynes D  Lee ML  Woolley AT  Tolley HD 《Biomicrofluidics》2011,5(2):21103

Planar nanochannels are fabricated using sacrificial etching technology with sacrificial cores consisting of aluminum, chromium, and germanium, with heights ranging from 18 to 98 nm. Transient filling via capillary action is compared against the Washburn equation [E. W. Washburn, Phys. Rev. 17, 273 (1921)], showing experimental filling speeds significantly lower than classical continuum theory predicts. Departure from theory is expressed in terms of a varying dynamic contact angle, reaching values as high as 83° in channels with heights of 18 nm. The dynamic contact angle varies significantly from the macroscopic contact angle and increases with decreasing channel dimensions.  相似文献   

Dial-in access to CD-ROM databases: beyond the local area network.     

P W Onsi  J A Capodagli  D K Hawkins 《Bulletin of the Medical Library Association》1992,80(4):376-379

Although it has meant additional work, CDLink has enhanced the productivity and effectiveness of the library's public services program. CDLink enables the library to offer dial-in access to databases, either in CD-ROM or other MS-DOS formats. The VAX MS-DOS connection is a cost-effective way to combine the benefits of remote access and multiple simultaneous use. From the user's perspective, CDLink provides free, twenty-four-hour remote access to databases in a friendly, menu-driven environment. For the library staff, the CDLink service represents the achievement of a long-awaited goal.  相似文献   

Changing and Explaining Behaviour by Reward     

Les Burwood  Carol Brady 《Journal of Philosophy of Education》1984,18(1):109-113

  相似文献   

Educational Philosophy and Theory: The first twenty years and more.     

Les Brown 《Educational Philosophy and Theory》1987,19(1):61-63

  相似文献   

THE STUDENT–TEACHER RELATIONSHIP QUALITY OF ABUSED CHILDREN          下载免费PDF全文

Jenna Montgomery Armstrong  Mary E. Haskett  Amy L. Hawkins 《Psychology in the schools》2017,54(2):142-151

Considering the association between children's quality of relationships with teachers and their academic adjustment, information pertaining to how abused children are functioning in their relationships with teachers could be useful in promoting their academic success—yet there has been limited research in this area. The purpose of this study was to use cluster analyses to explore within‐group differences in relational schemas and quality of student–teacher relationships for 70 abused children. Two clusters of abused children emerged, and as hypothesized, there were significant differences in student–teacher relationships for the two clusters. The cluster with more positive relational schemas had less conflict and less dependency reported by their teachers compared to the cluster with negative relational schemas. However, there were no differences between the clusters in terms of closeness with teachers. Implications for practice in schools are discussed.  相似文献