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在国内外有关交通流模拟研究成果的基础上,通过观测与对大量实测数据的统计处理,建立了一组信号控制干线道路系统交通流随机模拟模型,用计算机模特怕方法对具有显著离散事件性质的干线道路系统的交通容量进行了研究。 相似文献
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Regional partnerships have grown popular as mechanisms to address public goods that transcend local boundaries, but we know little about their effectiveness. For example, what impact do regional economic development partnerships (REDPs), cooperative organizations of local governments, nonprofits and business organizations have on the economies of metropolitan areas? This article employs survival analysis and multilevel growth curve models to examine how the emergence of regional partnership arrangements influences patterns of economic development in U.S. metropolitan areas. The results suggest that, whereas these organizations do not make a great difference in some metro areas, in densely populated and politically fragmented metropolitan areas personal incomes, business firms, and employment grew significantly with the emergence of REDPs. Furthermore, state level factors, such as intergovernmental grant funding, are found to have positive influences. In conclusion, we discuss regional partnerships as solutions to institutional collective action problems in economic development and other policy arenas. 相似文献
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An exact dynamic stiffness method is presented in this paper to determine the natural frequencies and mode shapes of the axially loaded double-beam systems, which consist of two homogeneous and prismatic beams with a distributed spring in parallel between them. The effects of the axial force, shear deformation and rotary inertia are considered, as shown in the theoretical formulation. The dynamic stiffness influence coefficients are formulated from the governing differential equations of the axially loaded double-beam system in free vibration by using the Laplace transform method. An example is given to demonstrate the effectiveness of this method, in which ten boundary conditions are investigated and the effect of the axial force on the natural frequencies and mode shapes of the double-beam system are further discussed. 相似文献
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QUAN WANG YING‐CHUN LIU JIAN LI WEI JIANG YONG‐JUN CHEN NING‐NING SONG 《Journal of food quality》2012,35(1):76-82
ABSTRACT
An indirect competitive enzyme‐linked immunosorbent assay with chemiluminescent (CL‐ELISA) detection for okadaic acid (OA) in mussel muscle was developed. A hybridoma cell line secreting monoclonal antibody against OA was established after immunization of BALB/c mice with artificially synthesized OA‐bovine serum albumin as antigen. Luminol solution was used as the substrate for horseradish peroxidase. The detection limit was 0.175 ng/g. The range of average fortified recovery was 91.8–102.6% when OA was spiked in mussel muscle at levels of 50, 160 and 800 µg/kg. The standard curve for OA showed good linearity over the concentration range of 0.08125–20 ng/mL. The cross‐reactivity with dinophysistoxin1 and saxitoxin was 51.82 and 0%, respectively. In a residue study, the results obtained by CL‐ELISA correlated well within those obtained using the commercial ABRAXIS kit (ABRAXIS, Warminster, PA). The developed method is therefore suitable for detecting the residues of OA in shellfish.PRACTICAL APPLICATIONS
Diarrhetic shellfish poisoning is a gastrointestinal syndrome that occurs in humans following the consumption of bivalve mollusks contaminated with OA with the main symptoms of diarrhea, nausea, vomiting and abdominal pain. OA widely exists at marine products and it is very important to develop a technique to monitor this toxin. In this study, a sensitive competitive indirect enzyme‐linked immunosorbent assay with chemiluminescence for determination of OA in mussel soft tissues was investigated. Chemiluminescent ELISA (CL‐ELISA) is a good alternative method for screening samples. This technique has the potential to improve the sensitivity of the immunoassays by at least two to three orders of magnitude compared with conventional colorimetric detection. 相似文献20.