汽车手动变速器六档设置的必要性分析

手动变速器是使用手拨动变速杆改变变速器内的齿轮啮合位置,进而改变传动比,改变发动机传到驱动轮上的转速和转矩,完成原地起步、爬坡、转弯、加速等功能。而六档的设置不仅可以提升换挡和行驶的平顺性、降低汽车的燃油消耗量、提升发动机的使用寿命,还能够更好地适应现代城市道路的实际交通现状和车主高速道路行驶的客观愿望等,因此六档(前进挡)的设置就显得尤为必要。     

管子智能生产线数字化管理系统设计

为实现管子生产过程的智能化,设计一种高效的管子智能生产线数字化管理系统。涉及企业ERP系统、船舶中日程计划排程系统、供应链系统、车间MES系统、高级排程APS系统、设备监控SCADA系统、立体库管理WMS系统、车间拉料LES系统等先进的信息化管理系统,配合先进的生产设备和合理的生产线布置,可以有效节约生产成本,提高车间的生产效率,成为管子智能化生产的最佳示范车间,具有广阔的实际应用前景。     

基于扩展状态观测器和滑模控制的双离合器自动变速器起步自适应控制

双离合器自动变速器（Dual Clutch Transmission,DCT）随着服役时间的增加离合器性态会发生变化导致起步性能下降,为降低离合器性态变化对起步性能的影响,提出一种基于扩展状态观测器和滑模控制的DCT起步自适应控制方法。首先,建立DCT起步动力学模型、发动机模型和液压控制系统模型;将DCT起步问题转化为参考轨迹跟踪问题,通过工况识别并利用极小值原理获得了不同起步工况的参考轨迹;在DCT起步动力学模型中将与离合器性态变化相关的项定义为不确定项,设计扩展状态观测器对不确定项进行估计,同时结合自适应滑模控制器,获得了起步发动机转矩和离合器油压的自适应控制率;为了跟踪发动机转矩和离合器油压的自适应控制率,设计了发动机转矩跟踪控制器,同时对液压系统采用了PID闭环控制;通过MATLAB/Simulink平台仿真以及台架试验验证所提出的DCT起步控制方法对离合器性态变化的自适应效果。研究结果表明：所提出的起步自适应控制方法能够有效避免由离合器性态变化导致的起步延时,同时1挡缓起步和急起步的仿真冲击分别减小了53.11%和43.42%,试验起步冲击分别减小了35.66%和30.31%。     

高海拔特长隧道低压低氧环境施工控制技术研究——供氧技术标准、关键通风技术、施工人员组织、施工装备效率

为解决高海拔地区低压和低氧环境带来的隧道施工供氧、通风等技术难题,采用现场试验及测试的方法,对高海拔隧道施工人员缺氧状况、供氧效果、机械排污量等进行研究,结合理论推导及数值计算,得到如下结果:人体的缺氧危险等级分为严重缺氧(Ⅰ)、缺氧(Ⅱ)、存在缺氧危险(Ⅲ)和不缺氧(Ⅳ)4级;基于肺泡氧分压与氧气体积分数关系的不同缺氧等级下的氧气体积分数控制标准;不同海拔CO体积分数控制标准模型;基于风管开口处流量理论的风管漏风率海拔修正系数计算公式;风机风压、功率的海拔修正系数公式;考虑人体劳动的平均能量代谢率海拔修正系数的不同海拔下施工人员劳动强度指数及强度等级。     

Efficiency in Nigerian ports: handling imprecise data with a two-stage fuzzy approach

This article is focused on assessing the efficiency of six major Nigerian ports from 2007 to 2013 by applying a two-stage fuzzy-based methodology adequate to handle imprecise data. More precisely, fuzzy data envelopment analysis models for traditional assumptions with respect to scale returns are employed to assess the productivity of Nigerian ports over the course of time. In the second stage, fuzzy regressions based on different rule-based systems are used to predict the relationship of a set of contextual variables on port efficiency. These contextual variables are related to different aspects of port service level, berth utilization, accessibility, cargo type, and operator type. The results reveal the impact of operator and cargo type on efficiency levels. Policy implications for Nigerian ports are derived.     

Will a higher free-flow speed lead us to a less congested freeway?

An approach based on cell transmission model (CTM) is proposed to estimate the impact of variable free-flow speeds (FFS) on the performance of a freeway system. Based on the basic CTM, four typical freeway control strategies consisting of non control, local ramp metering, coordinated ramp metering and global control are first formulated. Then the method of adjusting model parameters to the changed free-flow speeds is presented. Among the adjustments, an experimental function based on Fan and Seibold (2014) is proposed to change the jam density. Several useful measures are defined to estimate and compare the performances of different freeways. The following three main observations are obtained from numerical experiments. (a) With the gradually increasing FFS, the throughput of freeway will increase at the beginning and then change to decrease. (b) With the increasing FFS, the average delay of vehicles will decrease at the beginning and then change to increase. (c) A series of free-flow speeds associate with the best performance of freeway. These observations are theoretically analyzed through investigating the location and capacity of bottleneck. Study shows that in general the actual bottleneck capacity will increase at the beginning and then change to decrease with the continually increasing FFS. In view of the positive correlation between traffic delay and bottleneck capacity, the theoretical analysis confirms the numerical observations. The findings of this study can deepen the understanding of freeway systems and help management agents adopt proper measures to improve the performance of the whole system.     

基于通勤模式的都市圈中心结构判别研究

面对日益严重的城市交通问题，城市管理者尝试从城市空间规划层面引导交通出行模式的转型，调节供需关系，缓解交通问题，而中心结构识别作为城市空间规划的重要步骤，在分析方法与数据应用等方面仍然受限。本文利用百度位置数据挖掘出的都市圈通勤数据，采用基于网格的DBSCAN(Density-Based Spatial Clustering of Applications with Noise)密度聚类算法，识别出我国35个主要都市圈的中心布局，并根据5种通勤模式的理论模型和相应的量化指标对都市圈中心结构进行判别，最后对主要中心结构下影响通勤效率的因素进行回归分析。研究发现，虽然不同都市圈的中心布局差异明显，但大部分都市圈表现为非均衡多中心结构。不同中心结构的 分布呈现出一定的地域特征，单中心结构都市圈主要位于中西部城市，而约束扩散结构和均衡多中心结构都市圈大多是由东部沿海开放城市发展形成。城市规模与通勤时耗的相关性最为显著，职住平衡度对通勤时耗也有较大影响。上述研究结果为针对性地制定不同都市圈的资源配 置策略和通勤效率优化策略提供了有效支撑，对都市圈空间规划和交通可持续发展具有一定的理论价值和现实指导意义。     

基于乘客超越行为建模的航空登机效率分析

依靠缩短登机时间提升登机效率是降低航空周转成本的重要手段之一。乘客登机时间由登机策略及个体行为等因素共同决定。在采用特定登机策略登机过程中，发生阻塞导致队列行进缓慢时，队列内的乘客可能采取超越行为提升自身行进速度，从而影响登机效率。针对乘客这种超越行为建立微观仿真模型，采用元胞自动机模拟不同登机策略下的乘客登机过程，比较超越行为对不同登机策略效率的影响程度，量化考虑乘客超越行为时登机乘客携带行李比例、登机放行间隔，以及客座率等情景下登机策略的效率。结果表明：在考虑超越行为后，原本不考虑超越行为时登机时间越长策略的登机时间缩减比例越高，乘客行走干扰延误的降低是登机时间缩减的主要原因。在乘客携带行李数量较多或乘客放行间隔较短的情景下，从靠窗到过道依次登机策略的效率优于倒金字塔式策略；在客座率70%的情景下，分4种次序从后到前登机的策略是按列次序登机的最佳策略。     

A cell transmission model for dynamic lane reversal with autonomous vehicles

Autonomous vehicles admit consideration of novel traffic behaviors such as reservation-based intersection controls and dynamic lane reversal. We present a cell transmission model formulation for dynamic lane reversal. For deterministic demand, we formulate the dynamic lane reversal control problem for a single link as an integer program and derive theoretical results. In reality, demand is not known perfectly at arbitrary times in the future. To address stochastic demand, we present a Markov decision process formulation. Due to the large state size, the Markov decision process is intractable. However, based on theoretical results from the integer program, we derive an effective heuristic. We demonstrate significant improvements over a fixed lane configuration both on a single bottleneck link with varying demands, and on the downtown Austin network.     

Green port project scheduling with comprehensive efficiency consideration

ABSTRACT

Ports are an important driving force for world economic growth, but they consume considerable energy. The marine sector has proposed the development of green ports to achieve low-carbon sustainable development. This paper presents a green project scheduling model of port construction to optimize comprehensive economic and environmental efficiency. Various realistic constraints are considered, including investment scale, energy savings, emissions reduction, and project priority. Comprehensive efficiency involves cost reduction, energy savings, emissions reduction, and other efficiency goals. The problem is formulated as an integer program and is solved using CPLEX in a general algebraic modeling system (GAMS). We use a representative port in China as a case port in solving its green project scheduling. The results show that the port can save 6,527 tons of standard coal, reduce 40,875 tons of CO₂, and save 49 million yuan per year in the five-year implementation period. The payback in investing in these green projects is less than six years. From an economic and environmental perspective, the comprehensive efficiency achieved is significant.