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71.
72.
K.C. Adiga Robert F. Hatcher Jr Ronald S. Sheinson Frederick W. Williams Scott Ayers 《Fire Safety Journal》2007
Computational fluid dynamics (CFD) calculations were carried out to design total flooding fire tests in a 28 m3 compartment for an ultra fine water mist (<10 μm). The exit momentum of the mist produced by a proprietary ultrasonic generator technology was extremely low with a mist discharge velocity below 1 m/s. The mist was discharged with multiple floor outlets equally spaced around the centrally located 120 kW pool-like gas fire. The transport of mist and its interaction with the fire was simulated by Fluent, a commercial CFD model. Lagrangian Discrete Phase Model (DPM) was used for droplets. Simulation predicted extinguishment within 10 s with a mist delivery rate of 1 l/min. However, in total flooding fire tests conducted, extinction times were more than 5 min. Additional computations approximating the ultra fine mist (UFM) as a dense gas agreed well with the observed transport timescales of minutes indicating that UFM behaves like a gas. Further, the mist–fire interaction needs a multi-phase Euler–Euler approach with a droplet vaporization model. 相似文献
73.
74.
F.Michael Bartlett 《Structural Safety》1997,19(4):397-410
A two-step method for converting a concrete core compression test result to the in-place strength of the corresponding volume of concrete is presented. The strength of a non-standard core is first converted to the equivalent strength of a standard core, and then the standard core strength is converted to the equivalent in-place strength. Strength correction factors required for these conversions, obtained from weighted linear and nonlinear regression analyses presented elsewhere, are summarized. The accuracy of the predicted in-place strength is affected by the inherent error of the core strength measurement itself, and by the uncertainty of the various strength correction factors. It is shown that confidence intervals on the estimates of the strength correction factors obtained by regression analysis underestimate the true model error because the underlying models are imperfect. Instead, the accuracy of the strength correction factors is determined by a weighted regression analysis of ratios of observed-to-predicted values which accounts for the non-uniform variances of the dependent and independent variables. The coefficient of variation of the in-place strength predicted from a test of a 100 or 150 mm diameter core is between 4 and 5.5.%. If the in-place strength is predicted from a test of a 50 mm diameter core, the coefficient of variation of the predicted in-place strength is approximately 12.5%. These error estimates do not account for possible variation of in-place strength throughout the volume of the element being cored. 相似文献
75.
Mechanisms and models for anaerobic granulation in upflow anaerobic sludge blanket reactor 总被引:16,自引:0,他引:16
Upflow anaerobic sludge blanket (UASB) reactor has been employed in industrial and municipal wastewater treatment for decades. However, the long start-up period required for the development of anaerobic granules seriously limits the application of this technology. In order to develop the strategy for rapid UASB start-up, the mechanisms for anaerobic granulation should be understood. This paper attempts to provide a up-to-date review on the existing mechanisms and models for anaerobic granulation in the UASB reactor, which include inert nuclei model, selection pressure model, multi-valence positive ion-bonding model, synthetic and natural polymer-bonding model, Capetown's model, spaghetti theory, syntrophic microcolony model, multi-layer model, secondary minimum adhesion model, local dehydration and hydrophobic interaction model, surface tension model, proton translocation-dehydration theory, cellular automaton model and cell-to-cell communication model. Based on those previous works, a general model for anaerobic granulation is also proposed. It is expected that this paper would be helpful for researchers to further develop a unified theory for anaerobic granulation and technology for expediting the formation of the UASB granules. 相似文献
76.
本讨论了如何将人们在结构分析模型化处理方面的大量经验和理论分析结果,用知识库表达出来,借此提出了一种基于知识的工程机械结构分析模型化方法。 相似文献
77.
介绍了依托AutoCAD平台计算不规则设计面土方量的方法,并提出通过对开挖前后2次观测数据分别建模并相互叠加来找出填挖线的技巧. 相似文献
78.
Teaching construction project management with BIM support: Experience and lessons learned 总被引:1,自引:0,他引:1
Forest Peterson Timo HartmannRenate Fruchter Martin Fischer 《Automation in Construction》2011,20(2):115-125
This paper presents experiences and lessons learned during the introduction of Building Information Models (BIM) in construction engineering project management courses. We illustratively show that the introduction of BIM-based project management tools helped the teachers of two courses to develop more realistic project-based class assignments that supported students with learning how to apply different formal project management methods to real-world project management problems. In particular, we show that the introduction of BIM allows educators to design a class project that allowed the use of more realistic cases that better simulate real-world project conditions, helped students to learn how different project management methods integrate with each other, integrate change management tasks in a class assignment, and learn how to optimize project plans. 相似文献
79.
An often-noted feature of activated sludge settleability is the existence of a threshold content of filamentous bacteria, below which filaments have a relatively small effect on settleability, and above which settleability is much more sensitive to filament content. This concept has historically been based on an apparent inflection point in settleability/filament content curves. However, this was demonstrated to be an artifact of data presentation on semi-logarithmic scales. Analyses of several published data sets indicated that there was little or no evidence of a threshold effect when data were presented on linear scales, particularly around the 150 mL/g sludge volume index (SVI) "threshold". Rather, there appears to be a generally continuous (and often nearly linear) relationship between filament content and SVI, suggesting that the threshold effect, as commonly perceived, is not accurate. A modified empirical model of filament content and settleability was also presented. 相似文献
80.
从诞生的历史过程出发,论述了我国城市规划设计单位改革的宏观环境以及转轨的基本国情,诊断了我国城市规划设计单位体制改革的主要瓶颈因素,提出了体制改革的若干建议。 相似文献