Improved Speed Estimation From Single-Loop Detectors With High Truck Flow

Single-loop detectors are the most common sensors employed by freeway traffic management agencies. The data are used for traffic management and traveler information. Single-loop detectors can only measure flow and occupancy. Although speed is often the most useful metric, it can only be estimated at conventional single-loop detectors. Typically this estimate comes from the quotient of flow and occupancy multiplied by the fixed, assumed average effective vehicle length. This conventional approach is limited because the actual average effective vehicle length will vary from sample to sample. Many researchers have proposed alternatives to address this problem, and although many of the methods work well under normal conditions, there has been limited research into methods that yield reliable estimates under heavy truck traffic. Heavy truck flows may arise as a function of location or time of day, for example, with proximity to a trucking facility or in early mornings when the number of passenger vehicles drops, respectively. This article presents a new methodology to estimate speed from single-loop detectors in conditions where trucks comprise a large percentage of the fleet. While the focus is on single loop detectors, the work is equally applicable to side-fire microwave radar detectors that emulate single-loop detectors.     

柴油机油液光谱分析中换油干扰的处理

介绍了油液监测方式中的光谱分析方法,分析了原子发射光谱分析过程中润滑油更换对光谱分析数据产生的影响.以润滑油样中光谱分析的Fe元素为例,就换油产生数据分析干扰,讨论了直接测量、线性回归、Hermite、灰度模型等干扰消除方法.结果表明:直接测量法最简单,但修正结果最不理想;线性回归法受样本数据量的影响;Hermite法...     

车辆扰动下高架道路声屏障风荷载的数值模拟

对车辆扰动下高架道路声屏障屏体表面风荷载进行了数值模拟分析,获得了车辆经过时作用于屏体表面的典型的风压荷载时程。通过参数分析给出了屏体不同位置风压荷载的差异及原因。通过对屏体表面极值风压荷载的深入分析得出：现行采用声屏障所在地区50年一遇基本风压作为其设计控制荷载是不合理和不安全的。     

From suspended particles to strata: The fate of terrestrial substances in the Gaoping (Kaoping) submarine canyon

The river–sea system consisting of the Gaoping (new spelling according to the latest government's directive, formerly spelled Kaoping) River (KPR), shelf, and Submarine Canyon (KPRSC) located off southern Taiwan is an ideal natural laboratory to study the source, pathway, transport, and fate of terrestrial substances. In 2004 during the flood season of the KPR, a system-wide comprehensive field experiment was conducted to investigate particle dynamics from a source-to-sink perspective in the KPRSC with the emphasis on the effect of particle size on the transport, settling, and sedimentation along the pathway. This paper reports the findings from (1) two sediment trap moorings each configured with a Technicap PPS 3/3 sediment trap, and an acoustic current meter (Aquadopp); (2) concurrent hydrographic profiling and water sampling was conducted over 8 h next to the sediment trap moorings; and (3) box-coring in the head region of the submarine canyon near the mooring sites. Particle samples from sediment traps were analyzed for mass fluxes, grain-size composition, total organic carbon (TOC) and nitrogen (TN), organic matter (OM), carbonate, biogenic opal, polycyclic aromatic hydrocarbon (PAH), lithogenic silica and aluminum, and foraminiferal abundance. Samples from box cores were analyzed for grain-size distribution, TOC, particulate organic matter (POM), carbonate, biogenic opal, water content, and ²¹⁰Pb_ex. Water samples were filtered through 500, 250, 63, 10 µm sieves and 0.4 µm filter for the suspended sediment concentration of different size-classes.Results show that the river and shelf do not supply all the suspended particles near the canyon floor. The estimated mass flux near the canyon floor exceeds 800 g/m²/day, whose values are 2–7 times higher than those at the upper rim of the canyon. Most of the suspended particles in the canyon are fine-grained (finer than medium silt) lithogenic sediments whose percentages are 90.2% at the upper rim and 93.6% in the deeper part of the canyon.As suspended particles settle through the canyon, their size-composition shows a downward fining trend. The average percentage of clay-to-fine-silt particles (0.4–10 µm) in the water samples increases from 22.7% above the upper rim of the canyon to 56.0% near the bottom of the canyon. Conversely, the average percentage of the sand-sized (> 63 µm) suspended particles decreases downward from 32.0% above the canyon to 12.0% in the deeper part of the canyon. Correspondingly, the substrate of the canyon is composed largely of hemipelagic lithogenic mud. Parallel to this downward fining trend is the downward decrease of concentrations of suspended nonlithogenic substances such as TOC and PAH, despite of their affinity to fine-grained particles.On the surface of the canyon, down-core variables (grain size, ²¹⁰Pb_ex activity, TOC, water content) near the head region of the canyon show post-depositional disturbances such as hyperpycnite and turbiditic deposits. These deposits point to the occurrences of erosion and deposition related to high-density flows such as turbidity currents, which might be an important process in submarine canyon sedimentation.     

液压机械无级变速器速比自抗扰控制研究

本文中设计了一种单行星排液压机械无级变速器,并为提高其速比跟踪控制性能,提出一种带前馈的自抗扰控制算法,以实现速比的跟踪控制.首先建立系统数学模型,通过传动系统转速关系的理论分析,得到前馈控制量,进一步采用自抗扰控制器对速比进行闭环控制.接着建立系统仿真平台和原型样车,通过仿真和试验对设计的带前馈自抗扰速比控制器进行验...     

车速控制系统自适应油门控制器设计

在分析非线性车辆纵向动力学模型及简化模型基础上，采用一种简化非线件模型设计自适应油门控制器，并应用李亚谱诺夫理论证明了传动系统存在动态过程时控制系统的稳定性。通过对基于简化线性和非线性模燃的自适应控制器的仿真研究，结果表明后者具有更好的收敛性。试验结果也进一步表明，基于非线性模型的自适应控制器可以通过自适应调节减小参数不确定造成的干扰，当传动系统存在动态过程时可以保证车速跟踪误差有界。     

山区河流航道整治施工对水生态环境的影响

山区河流航道整治一般采取筑坝、疏浚、炸礁、护岸等工程，在施工中不可避免对现状水生态环境造成扰动。以岷江下游航道整治一期工程为例，通过对代表性河段施工前后的水质、浮游生物、底栖动物、鱼类等种类和资源量开展现场监测，研究发现：施工前后水体化学需氧量、五日生化需氧量、氨氮、总磷、石油类、悬浮物的浓度有所升高，但均未超过相关标准限定值；藻类、水生维管束植物、浮游动物、底栖动物、鱼类等施工前后无明显减少。因此通过合理的时间、空间的施工避让，航道整治施工对山区河流水生态环境的影响较小。