Cardiovascular disease outcomes have been associated with exposure to ambient particulate matter (PM) air pollution in many epidemiological studies. Experimental studies have revealed potential mechanisms behind the epidemiological results and many of these studies have revealed changes in the expression of important genes in key biological pathways with exposure to air pollution from fossil fuel combustion. Few epidemiological studies have examined this. We hypothesized that blood cell gene expression levels along biological pathways relevant to cardiovascular outcomes would be associated with traffic-related air pollutant exposures in elderly subjects with coronary artery disease. Available data were collected in a cohort panel study funded by the National Institutes of Health, National Institute of Environmental Health Sciences. Gene expression data were available for 43 subjects with up to 12 weekly repeated measures conducted in three of the four retirement communities in the Los Angeles Air basin where the exposure measurement work took place. Whole blood samples were collected weekly, RNA was isolated and then it was reversed transcribed into complementary DNA for subsequent gene expression analysis using the polymerase chain reaction method. Candidate genes (35) were selected a priori based on biological function and reported pollutant exposure effects. Exposure measurements were conducted in the indoor and outdoor environment of each community and included daily size-fractionated PM mass and PM organic chemical composition, including polycyclic aromatic hydrocarbons (PAH).

关键词：大气；威力污染物；基因表达

查看摘要 索取原文[96页]

Retaining wall using steel frame and fill material is a kind of the cellular structure. The cellular structure using a fill material has a number of advantages such as excellent constructability in the short term, permeability, and decrease in effects of groundwater fluctuations after the end of construction. Because this structure is discontinuity, it is quite difficult to apply analysis in finite element methods. In addition, there are no evaluation techniques to establish its shear resistance clearly. In order to solve the issue, this paper presents that shear resistance analysis is performed by introducing displacement incremental analysis into the distinct element method. It enables not only to model continuous and discontinuous structure, but also to perform static and dynamic analysis. The results of analysis are compared with experimental results of the retaining wall with a steel frame and fill materials.

关键词：细胞结构；剪切阻力；填充材料；离散元法

查看摘要 索取原文[6页]

This paper presents a comparison of test results on the material behavior of zero-slump, dry-cast steel and synthetic fiber-reinforced concrete. ASTM C1609 flexural beam test and ASTM C39 compressive strength cylinder tests were conducted for various fiber dosages of each type of synthetic and steel fiber. Synthetic and steel fiber dosages ranged from 4 lb/yd~3 to 18 lb/yd~3 and 22 lb/yd~3 to 88 lb/yd~3, respectively. From these tests, material properties were found that included compressive strength, first-peak load, peak load, modulus of rupture, and specimen toughness. These values were all within the range of conventional design parameters used in concrete structures. ASTM beam load-deformation plots were obtained for each fiber beam to show the fiber behavior and strengthening after the initial crack.

关键词：钢铁；合成纤维材料；混凝土材料

查看摘要 索取原文[6页]

Although steel orthotropic deck is currently the most widely adopted solution for long-span bridges, the poor adhesion to the upper asphalt layers still represents a serious problem without a clear solution. In recent decades many techniques that involve the use of special bituminous bonding coats, reinforced asphalt membranes, net-reinforced steel deck surfaces, or epoxy asphalt binders have been applied, with varying results, to improve the level of adhesion of the asphalt pavement to the steel surface. In this experimental study, two such techniques were adopted to investigate the shear resistance of steel-asphalt pavement systems. The first technique used epoxy asphalt both as a bonding coat and as a binder of the upper asphalt layer, while the second technique involved the use of a reinforced asphalt membrane that was applied on the steel deck before overlaying with conventional hot-mix asphalt (HMA). The Ancona Shear Testing Research and Analysis shear test device was used to evaluate the shear resistance of different types of HMA-steel interfaces and to investigate the effects of temperature and normal stress. The results have been compared with the shear properties of bitumen-coated interfaces, studied in previous research. The results showed that epoxy asphalt guaranteed high performance regardless of the test temperature. However, the shear resistance of the system with the asphalt membrane was lower than with the epoxy asphalt, although it was higher than the resistance of bitumen-coated interfaces at high temperatures.

关键词：正交异性钢桥；钢铁；沥青膜

查看摘要 索取原文[6页]

It is well established that GHG emissions must be reduced by 50% to 80% by 2050 in order to limit global temperature increase to 2DGC. Achieving reductions of this magnitude in the transportation sector is a challenge and requires a multitude of policies and technology options. The research presented here analyzes three scenarios: changes in the perceived price of travel, land-use intensification, and increases in transit. Elasticity estimates are derived using an activity-based travel model for the state of California and broadly representative of the U.S. The VISION model is used to forecast changes in technology and fuel options that are currently forecast to occur in the U.S., providing a life cycle GHG forecast for the road transportation sector. Results suggest that aggressive policy action is needed, especially pricing policies, but also more on the technology side. Medium- and heavy-duty vehicles are in particular need of additional fuel or technology-based GHG reductions.

关键词：大气；环境保护；温室气体

查看摘要 索取原文[60页]

Improved software interoperability is key to realizing more fully the potential benefits of integrated and accelerated project delivery in a way that also somehow ensures product quality. The increasing appeal of three-dimensional (3-D) building information modeling (BIM) notions applied to bridges [known as bridge information modeling (BrIM)] motivates the need for principled prescriptions of associated electronic data exchanges between various project stakeholders and the various software applications that they use. Such data exchanges must be sufficiently precise to facilitate detailing for fabrication and construction while being sufficiently concise to facilitate parametric modeling and thereby avoid needless data duplication. The highway geometry to which bridges must conform distinguishes BrIM from the building column grid orientation of BIM at the outset of the bridge life cycle. In contrast to the overdefined highway geometry in the LandXML data exchange standard, a 3-D control curve is defined, presented, illustrated, and recommended as the basis for parametric data exchange suitable through the life cycle of steel Ⅰ-girder bridges on (straight and) curved alignments. This 3-D control curve combines in a single curve the traditional horizontal control line and profile grade line that bridge structural engineers receive from highway designers to define bridge geometry. Data exchanges associated with three distinct stages in the life cycle of a steel bridge are defined and illustrated: analysis and design, detailing for fabrication, and erection and construction. The data exchange based on a 3-D control curve provides the data integrity required through the life cycle of a steel bridge.

关键词：三维参数；钢铁；曲线钢桥

查看摘要 索取原文[8页]

Based on node test and finite element analysis results of four different structural form enhanced nodes,failure modes,hysteretic behavior,bearing capacity,ductility and energy dissipation capacity of nodes are analyzed comprehensively and comparatively for more in-depth exploration about the seismic performance of symmetric enhanced nodes.The results showed that all the symmetric enhanced nodes have full hysteretic curve and energy dissipation capacity.On the whole,The flange-plate reinforced node exhibit better seismic performance.

关键词：钢框架；加强节点；循环加载试验；有限元分析

查看摘要 索取原文[5页]

Using a 1984 benchmark experiment, MCNP6 replicated the neutron flux and neutron protection factor (NPF) measurements of an iron box, which simulated a basic military vehicle, resulting in less than 5% difference from the published results. Additionally, the neutron flux spectrum of a 239 PuBe source was characterized using a Bonner Sphere Spectrometer (BSS) and the solution unfolded using the Maximum Entropy Deconvolution (MAXED) program, producing a X2/df of 0.97. Utilizing a steel box provided by the DTRA, measurements of neutron flux from a D-D neutron accelerator were recorded via BSS inside and outside of the box. Both flux spectra were unfolded through MAXED using MCNP6 computations as a priori, which resulted in X2/df values of 0.86 and 0.91, respectively. NPF assessments of the steel box were then conducted using experimental and MCNP6 flux spectra for the box, as well as H*(10) scaling, with final results differing by less than 1%. MAXED software was leveraged for all flux spectrum unfolding, incorporating updated BSS response functions generated within this research from MCNP6. This experiment and its conclusions strongly support the verification and validation of MCNP6 for modeling NPF assessments of military vehicles.

关键词：中子通量；中子保护因子；中子能谱；钢铁

查看摘要 索取原文[104页]

The development length of reinforcements embedded into ultra-high performance concrete (UHPC) can be significantly shorter than the lengths normally associated with conventional concrete. Shortening the development length of prestressing strand can allow for a redesign of some structural systems, including spliced girder and continuous-for-live-load bridges. Ultra-high performance concrete (UHPC), when used in field-cast connections between prefabricated bridge elements, can create robust connections which emulate monolithic components. This study investigated the development length of 0.5 and 0.6 inch (12.7 and 15.2 mm) diameter untensioned prestressing strands embedded in steel fiber and PVA fiber reinforced UHPC. The volumetric fiber content was 2 percent. A novel tension test method allowed for replication of the tension-tension stress state that would occur when two strands are lap spliced within a connection between two linear elements. The results suggest that, for the steel fiber reinforced UHPC, the 0.5 inch (12.7 mm) diameter strands can be fully developed within 20 inches (0.51 m) and the 0.6 inch (15.2 mm) diameter strands can be fully developed in approximately 24 inches (0.61 m). The 0.5 inch (12.7 mm) diameter strands can be fully developed in the PVA fiber reinforced UHPC in approximately 36 inches (0.91 m).

关键词：高强度混凝土；钢绞线;桥梁；纤维增强混凝土

查看摘要 索取原文[46页]

In August 2010, Midwest Roadside Safety Facility (MwRSF) developed and crash tested a low-cost, energy-absorbing bridge rail for the Manual for Assessing Safety Hardware (MASH) TL-3 applications. This low-cost bridge rail was designed to be compatible with the Midwest Guardrail System (MGS) such that an approach transition would not be required between the two barriers. It was desired that the system minimize bridge deck and rail costs. As part of this project, several concepts for an energy-absorbing bridge post were developed and tested. These concepts included strong-post systems designed with plastic hinges and weak-post systems designed to bend near the attachment to the bridge deck. The final post concept incorporated S3 OE 5.7 steel sections designed to yield at their bases. These posts were located on 6 ft-3 inches on center. A W-beam section was used as the rail element and was attached to the posts with a bolt designed to break during and impact event. Two full-scale crash tests were performed according to the TL-2 impact conditions provided in MASH. The new bridge rail system successfully met all the safety performance criteria for MASH TL-2. The Texas Type T631 Bridge Rail was developed as a low-cost, energy absorbing bridge rail system for TL-2 applications. Many of the features used for the system tested at Midwest Roadside Safety Facility for TL-3 were incorporated into the design developed for this project for MASH TL-2 application. The TxDOT Type T631 Bridge Rail designed and developed for this project was evaluated under MASH TL-2.

关键词：大桥护栏；碰撞测试；钢铁

查看摘要 索取原文[102页]