根据修正的双参数法求解桩基的水平内力

近年来关于桩基水平内力的研究已取得一系列新的成果,虽然采用多种方法计算的基桩水平内力与实测值比较接近,但其计算过程比较复杂,采用的计算参数多由土工试验得出,受人为因素影响较大。为进一步简化桩基水平内力计算并提高计算精度,根据修正的双参数法和有限差分原理推导桩基水平内力的计算公式,可求得桩身各节点的水平内力。     

海洋立管的模态及参数敏感性分析

为分析海洋立管受不同形式的轴向张力作用时的模态求解问题,用哈密尔顿原理建立理论模型,讨论模态的计算方法,并分析相关参数对结果的影响。结果表明,在相同的张力因子下,随着立管长度增大其固有频率主要受张力的控制;在深水中因表观重力引起的沿轴向张力的线性变化不可忽略,对频率和振型都有重要影响,张力因子的增大使频率提高,这种影响对结构长度变化敏感;频率随附加水质量系数的增大而降低。     

南海FLNG上部模块总体布局方案研究

FLNG在南海深水气田开发中应用前景广阔,应加强对其设计技术的研究.本文结合调研和项目经验,总结FLNG上部模块总体布置原则和规范,研究布局影响因素,并提出南海FLNG布局建议.FLNG上部模块设计时,应符合安全、经济、合理的原则,并遵守船级社和本行业在总体、工艺、安全等方面的规范;在选择布局方案时,应重点考虑系泊、外输、解脱、工艺方案等4个因素的影响;对于南海FLNG总体布局方案,采用旁靠时建议按从船首到船尾"单点-火炬-预处理-液化-外输-电站/公用-生活楼"布局,采用尾靠时建议按"生活楼-单点-电站/公用-预处理-火炬-液化-外输"布局.本研究成果可以为今后开展南海FLNG上部模块设计提供参考.     

低噪声迷宫式控制阀设计原理及数值分析

在舰船水管路系统中,采用控制阀进行管路系统阻力匹配设计并实现低噪声配置。控制阀在水力激励下形成振动噪声并通过管路传递形成船外辐射噪声。为降低管路系统振动及船外辐射噪声,有必要进行低噪声控制阀的设计研制。该文提出了控制阀水力及声学设计方法,采用流体动力学数值方法进行了低噪声控制阀原理分析,验证了分流、多级和迷宫拐角式低噪声设计原理。基于低噪声设计原理设计了包含上层穿孔、中层多迷宫流道和下层少迷宫流道三部分重叠形成的阀套流通结构的分层迷宫式控制阀。阀内流场分析结果显示:阀套出流不均匀形成高速低压区域,易发生空化增大噪声;阀套腔体和阀套沿出流方向出口处形成大尺度漩涡结构,为主要噪声源区域。     

Multilane first-order traffic flow model with endogenous representation of lane-flow equilibrium

In this study, we develop a multilane first-order traffic flow model for freeway networks. In the model, lane changing is considered as a stochastic behavior that can decrease an individual driver’s disutility or cost, and is represented as dynamics toward the equilibrium of lane-flow distribution along with longitudinal traffic dynamics. The proposed method can be differentiated from those in previous studies because in this study, the motivation of lane changing is explicitly considered and it is treated as a utility defined by the current macroscopic traffic state. In addition, the entire process of lane changing is computed macroscopically by an extension of the kinematic wave theory employing IT principle; moreover, in the model framework, the lane-flow equilibrium curve is endogenously generated because of self-motivated lane changes. Furthermore, the parsimonious representation enables parameter calibration using the data collected from conventional loop detectors. The calibration of the data collected at four different sites, including a sag bottleneck, on the Chugoku expressway in Japan reveals that the proposed method can represent the lane-flow distribution of any observation site with high accuracy, and that the estimated parameters can reasonably explain the multilane traffic dynamics and the bottleneck phenomena uphill of sag sections.     

On macroscopic freeway merge behavior: Estimation of merge ratios using asymmetric lane flow distribution

Data from several freeway merges reveal that, contrary to some previous findings, merge ratio can vary within a site with respect to the merge outflow and that the existing merge ratio estimates based on lane counts are not able to predict this within-site variation. Furthermore, the merge ratios estimated based on two well-known merging principles, “fair-share” and “zipper,” are found to be inaccurate for merges where merging streams compete directly due to a lane drop. In light of these findings, we estimate merge ratios using lane flow distribution (LFD) to better predict between and within site variations of merge ratio. In addition, we propose a merging principle specific for merges with a single lane-drop. The model was developed to better represent observed non-uniform redistribution of merging flow not captured by the current merge ratio estimation methods and merging principles. Empirical observations show that the proposed methods are able to improve merge ratio estimates, reproduce within-site variations of merge ratio, and represent more accurately non-uniform redistribution of merging flow dependent on the merge geometry.     

小缸径低速柴油机加装EcoEGR系统设计与布置

某型火车滚装船布置2台小缸径低速柴油机加装经济型废气再循环（Economical Exhaust Gas Recirculation，EcoEGR）系统，以满足Tier Ⅲ排放要求。以该船为依托，对该类型主机及相应船舶管路与控制系统的原理设计、实船布置等进行介绍和深入分析，为后续或类似船舶的小缸径低速柴油机加装EcoEGR系统及设备设计与建造提供有价值的参考。     

主客观综合评价法在内河航道选汊中的应用

内河航道建设中在分汊河段面临汊道选择问题,尤其是大型内河航道建设因投资巨大且对河段航道格局有长期影响,选汊涉及的因素繁多且无法直接比较。以长江南京以下12.5 m深水航道福姜沙河段的选汊问题为例,在对不同选汊方案的港口适应性、通航组织风险、航行干扰、施工期运营期风险、航道服务水平、锚地便利性、投资及航道维护等方面分析的基础上,采用主客观综合评价法(CRITIC),建立多目标决策评价模型。根据模型计算结果对选汊方案优劣排序,并进行稳定性检验,得出福中+福北方案为最优选汊方案。     

Valuation of strategic options in public–private partnerships

This paper investigates the feasibility of and develops an economic valuation model for strategic options in Comprehensive Development Agreements (CDAs). A CDA is a form of public–private partnership whereby the right to price and collect revenues from toll roads is leased to a private entity for a long but finite period of time. In exchange, this provides local and state governments with a quick influx of cash and/or additional infrastructure. Uncertainty associated with such long-term leases is of substantial public concern. This paper examines five different strategic options, namely a buyout option, a conditional buyout option, a revenue-sharing option, and two types of minimum revenue guarantee options. The buyout option in particular could give the public sector additional control over the future use of leased facilities and address potential concerns regarding long-run uncertainty and possible unforeseen windfalls for the private sector. The paper’s contributions include the analysis, feasibility assessment and valuation of several strategic options, sensitivity analysis of the solutions, an economic consumer demand-based revenue model for purposes of cash flow simulation, and analysis of option price sensitivity to “moneyness”. The main conclusion is that strategic options can provide useful risk reduction, but generally have significant value relative to the lease itself. By scaling down payoffs, options could be realistically included in CDAs and other PPPs. For some parameter values, option values to the developer and public authority are offsetting, allowing for costless risk reduction.