Ecological conversion efficiency and its influencers in twelve species of fish in the Yellow Sea Ecosystem

The ecological conversion efficiencies in twelve species of fish in the Yellow Sea Ecosystem, i.e., anchovy (Engraulis japonicus), rednose anchovy (Thrissa kammalensis), chub mackerel (Scomber japonicus), halfbeak (Hyporhamphus sajori), gizzard shad (Konosirus punctatus), sand lance (Ammodytes personatus), red seabream (Pagrus major), black porgy (Acanthopagrus schlegeli), black rockfish (Sebastes schlegeli), finespot goby (Chaeturichthys stigmatias), tiger puffer (Takifugu rubripes), and fat greenling (Hexagrammos otakii), were estimated through experiments conducted either in situ or in a laboratory. The ecological conversion efficiencies were significantly different among these species. As indicated, the food conversion efficiencies and the energy conversion efficiencies varied from 12.9% to 42.1% and from 12.7% to 43.0%, respectively. Water temperature and ration level are the main factors influencing the ecological conversion efficiencies of marine fish. The higher conversion efficiency of a given species in a natural ecosystem is acquired only under the moderate environment conditions. A negative relationship between ecological conversion efficiency and trophic level among ten species was observed. Such a relationship indicates that the ecological efficiency in the upper trophic levels would increase after fishing down marine food web in the Yellow Sea ecosystem.     

Discrete dynamic models for freeway incident detection systems

This paper considers the problem of freeway incident detection within the general framework of computer‐based freeway surveillance and control. A new approach to the detection of freeway traffic incidents is presented based on a discrete‐time stochastic model of the form ARIMA (0, 1, 3) that describes the dynamics of traffic occupancy observations. This approach utilizes real‐time estimates of the variability in traffic occupancies as detection thresholds, thus eliminating the need for threshold calibration and lessening the problem of false‐alarms. Because the moving average parameters of the ARIMA (0, 1, 3) model change over time, these parameters can be updated occasionally. The performance of the developed detection algorithm has been evaluated in terms of detection rate, false‐alarm rate, and average time‐lag to detection, using a total of 1692 minutes of occupancy observations recorded during 50 representative traffic incidents.     

半干旱区路域边坡生态恢复初期土壤一植被演替研究

为了深入了解半干旱区路域边坡生态恢复初期土壤一植被系统演替特征,文章以山西太原绕城高速边坡生态修复示范工程为对象,结合对该示范工程边坡土壤一植被所开展的连续6年的野外定点生态监测实践,运用室外监测和室内数据分析,研究了土壤肥力、植被群落等特征指标的动态变化规律,为半干旱区公路边坡植被恢复提供参考依据。     

用索拱体系加固提载刚架拱桥的分析研究

提出一种拱索体系加固现有钢筋混凝土刚架拱桥的方法,并以一座典型桥梁为例,对其加固前后的力学性能进行了分析,结果表明这种加固方法使桥梁的跨中弯矩和挠度大为减少,承载能力明显提高,它是一种加固早期修建钢筋混凝土刚架拱桥的有效方法,具有一定的理论意义和工程实用价值。本文还对该加固方法的施工程序及斜拉索的合理索力进行了论述。     

公路建设项目环境监理监测指标体系研究

环境监测是环境监理进行现场监理和评价重要手段,是环境监理科学化、规范化和系统化的要求。根据公路建设项目特点,通过对常规环境监测指标的分析,提出了公路施工环境监理监测的重点性、全面性、代表性、持续性和简单性原则,并提出将SS、粉尘、Laeq和可回收固体废物的回收率做为公路施工期环境监理的污染监测指标,将生态保护度、土粒滞留时间和适时绿化率作为公路施工期环境监理的生态监测指标,并对粉尘、生态保护度、土粒滞留时间、适时绿化率、可回收固体废物的回收率的监测方法进行了说明。     

仿真技术应用于环形交叉口通行能力中的研究

本文运用仿真技术对环形交叉口的通行能力进行了研究,从微观的角度对影响通行能力的各关键参数进行了分析。仿真技术的优点保证了各种交通特性都能在标定通行能力中得到反映,因而相对于经验模型和分析模型更能体现其研究环行交叉口通行能力的合理性。     

复杂边界条件下土体极限承载力的荷载增量逼近求解

在拓展Bishop极限分析方法的基础上,采用坡脚反向虚拟菏载及垂直菏载增量逐次逼近的方法建立复杂几何边界条件下的土体极限承载力的计算方法,该方法求争简便,借助简单的计算机程序可求解任意几边界条件下的土体极限承载力,对坝堤极限堆物菏重、天然边坡顶部极限承载力等的计算有一定理论意义和实用价值。     

交叉口通行能力的综合计算法

交叉口通行能力的大小直接影响到整个路网效率，提高交叉口的通行能力是目前道路网的重要目标之一。然而，交叉口处固有的通行能力大小，是交叉口本身的特性所决定的，同时这也与车辆等诸多因素密不可分。本文引入交叉口极限通行能力的有序度的概念，为交叉口通行能力的计算给出一种简便而又通用的算法。     

快速路分、合流影响区交通特性及通行能力研究

分、合流区通行能力是影响快速路通行能力的重要因素之一,而分、合流影响区的通行能力是制约分、合流区通行能力的关键原因。文章从分析分、合流影响区内的车辆运行特性入手,根据北京、上海、广州等城市大量的实测数据,分别通过统计车头时距、速度-流量关系和饱和流时高频率出现的流率等方法推荐了快速路分、合流影响区的通行能力,为快速路分、合流区的交通规划和设计,交通组织和管理的改善提供了理论基础。     

生态防护技术在高速公路边坡防护中的应用

文章针对高速公路建设所带来的诸多环境问题,介绍生态防护技术在黄榆高速公路边坡防护中的应用,并通过对这些技术的使用效果进行比较、分析,提出了公路边坡防护中的一些不足以及仍需研究和解决的问题。