Enhanced, multi criteria based site selection to measure mobile source toxic air pollutants

A multi-criteria-based site selection process that was developed for the Las Vegas near-road study is used to select the most appropriate near-road measurement sites in the Detroit area. The study measures particulate matter with aerodynamic diameters ?2.5 μm and mobile source air toxic compounds, and to document the rationale for selecting or rejecting specific sites. An application of this multi-criteria decision analysis may be the recent US Environmental Protection Agency rule requiring the siting of NO₂ monitors within 50 m of major roads as well as siting for the measurement of community-wide NO₂ concentrations.     

数字狂徒

从21世纪开始,我们就半自愿半被迫地被推进数位的世界,一切原本连绵温暖的东西忽然间被分断成疏离的存在,菲林、黑胶唱片、信件等都被电脑里一连串的零一零一零一数字取代。芸芸众生之中,唯一不被数码攻陷的,便是高级腕表的世界。在这里,如果你戴着一枚数码跳字腕表,是会惹来鄙夷目光的。     

发展中国家机动化讨论

以中国、印度等为代表的广大发展中国家已进入快速机动化阶段.以此为背景,首先分析了发展中国家机动化发展的新现实,包括:提高了出行机动性,带来了大量的社会经济成本,增加了能源消耗,加剧了环境污染,同时面临发展资金不足、管理经验缺乏及资源分配不公等带来的社会问题.然后指出依靠交通运输技术的跨越式发展,未必能解决上述一系列问题...     

The effects of slow steaming on the environmental performance in liner shipping

The environment issue is one of the significant challenges that the liner shipping industry has to face. The International Maritime Organization (IMO) has set a goal to reduce greenhouse gas (GHG) emissions from existing vessels by 20–50% by 2050 and develop the Energy Efficiency Operational Indicator (EEOI) as a measure for energy efficiency. To achieve this goal, IMO has suggested three basic approaches: the enlargement of vessel size, the reduction of voyage speed, and the application of new technologies. In recent times, liners have adopted slow steaming and decelerated the voyage speed to 15–18 knots on major routes. This is because slow steaming is helpful in reducing operating costs and GHG emissions. However, it also creates negative effects that influence the operating costs and the amount of GHG emissions at the same time.

This study started with the basic question: Is it true that as voyage speed reduces, the operating costs and CO₂ emissions can be reduced at the same time? If this is true, liners will definitely decelerate their voyage speed themselves as much as possible so that they can increase their profits and improve the level of environmental performance. However, if this is not true, then liners will concentrate just on increasing their profits by not considering environmental factors. This led the authors to set out three objectives: (1) to analyze the relationship between voyage speed and the amount of CO₂ emissions and to estimate the changes by slow steaming in liner shipping; (2) to analyze the relationship between voyage speed and the operating costs on a loop; and (3) to find the optimal voyage speed as a solution to maximize the reduction of CO₂ emissions at the lowest operating cost, thus satisfying the reduction target of IMO.     

Computational model for analyzing the kinematics and compliance characteristics of a commercial vehicle’s front suspension system

This paper develops a computational model that can analyze the kinematics and compliance characteristics of the front suspension of a commercial vehicle. This computational model is called the flexible multi-body dynamic model because it is developed by interfacing the finite element model of the multi-leaf spring with the dynamic model of the front suspension. In this paper, the bump mode and roll mode tests are performed with a suspension parameter measuring device (SPMD). An excitation load for creating the bump mode and roll mode motion is applied on the left and right tires slowly in in-phase and out-of-phase modes. In the test, wheel rate, toe angle change, caster angle change, and camber angle change, which together represent the wheel alignment, are measured along with the longitudinal and lateral wheel center loci which together represent the wheel center trajectory change. The reliability of the developed computational model is verified by comparing the simulation results with the SPMD test results. The developed flexible multi-body computational model will provide useful information on kinematics and compliance characteristics in the earliest stages of the commercial vehicle design process.     

Current sensorless drive method for electric power steering

This paper proposes a current sensorless drive method by using the mathematical modeling of a surface-mounted permanent magnet synchronous motor (SPMSM) and a dead-time compensation method to reduce the calculated current error caused by differences between real output voltages and voltage commands. The proposed method is implemented by using only a processor algorithm internally, i.e., without any voltage-sensing circuit hardware, such as filtering circuits and current sensor feedback circuits. To show the effectiveness of the proposed method, MATLAB simulations are carried out with an Electric Power Steering (EPS) System containing an SPMSM, a motor drive system and a mechanical gear system. The result shows the validity of the proposed method.     

Impact of proposed federal limits on US bagged food aid shipments: reduction in MSF carrier profits—a risk assessment 1

This paper is a stochastic risk simulation of the impact of proposed federal tonnage limits on US Maritime Security Fleet (MSF) bagged food aid shipments. Only MSF (i.e. federally subsidized carriers/vessels for war, or emergencies) and non-MSF US carriers (therefore, at competitive disadvantage) can compete for such shipments—representing an indirect subsidy to both groups. To compensate, US Congress proposed a financial penalty (loss of voyage subsidy) on MSF carriers for food aid above a certain limit. Accordingly, certain carriers will be policy 'winners' (non-MSF—larger food aid shipments), and others 'losers' (MSF). By simulating loss-minimizing economic behaviour by MSF carriers—using five stochastic factors—I obtain losses substantially below those claimed by the MSF owners.

Simulated annual-average MSF profits reduction is $3.5 million—within a large confidence interval; if no carriers surrender their subsidies (as claimed by MSF owners), a reduction of $6.0 million. Only 16% of annual MSF voyages are affected by a 2,500-ton limit (3%; 5,000-ton limit). Minimizing losses, 25 (of 41 affected) annual MSF voyages replace 38,000 tons of food aid with 23,000 tons of other cargo—forgoing $2.1 million in yearly direct subsidies. Two assumptions explain most of this simulated loss reduction.     

Impact of interviewing by proxy in travel survey conducted by telephone

Telephone‐interview surveys are a very efficient way of conducting large‐scale travel surveys. Recent advancements in computer technology have made it possible to improve upon the quality of data collected by telephone surveys through computerization of the entire sample‐control process, and through the direct recording of the collected data into a computer. Notwithstanding these technological advancements, potential sources of bias still exist, including the reliance on an adult member of the household to report the travel information of other household members. Travel data collected in a recent telephone interview survey in the Toronto region is used to examine this issue. The statistical tool used in the research was the Analysis of Variance (ANOVA) technique as implemented within the general linear model framework in SAS. The study‐results indicate that reliance on informants to provide travel information for non‐informant members of their respective households led to the underreporting of some categories of trips. These underreported trip categories were primarily segments of home‐based discretionary trips, and non home‐based trips. Since these latter two categories of trips are made primarily outside the morning peak period, estimated factors to adjust for their underreporting were time‐period sensitive. Further, the number of vehicles available to the household, gender, and driver license status respectively were also found to be strongly associated with the underreporting of trips and thus were important considerations in the determination of adjustment factors. Work and school trips were found not to be underreported, a not surprising result giving the almost daily repetitiveness of trips made for these purposes and hence the ability of the informant to provide relatively more precise information on them.     

Active Suspension Control to Improve Vehicle Ride and Handling

In practice most active vehicle suspension work can be traced to two sources, Lotus' modal control and Karnopp's skyhook damper. A model is developed which allows comparison of different active suspension control algorithms. The Lotus modal control algorithm is reviewed, and compared with Karnopp's skyhook damper. It is shown that a tight inner closed loop allows the Lotus algorithm to achieve the inertial damping described by Kamopp for a single comer or quarter car. It is suggested that to achieve simultaneously high inertial damping and good disturbance rejection an inner force loop is desirable. A vehicle control scheme is presented which combines the Lotus modal decomposition with Karnopp's skyhook damper, allowing nearly optimal ride and simultaneously permitting modification of vehicle handling properties.