Truck versus pipeline transportation cost analysis of wastewater sludge

Domestic and industrial sludge generated at wastewater treatment facilities is considered a potential biomass source for producing biodiesel. However, transportation of large amounts of sludge from wastewater treatment facilities to a biorefinery is expensive. The objective of this paper is to identify the proper transportation mode to use as a function of the volume shipped and transportation distances. Currently, sludge is mainly shipped by truck and pipeline. We estimated that the fixed and variable cost components of pipeline transportation for a volume such as 480 m³/day and a distance of 100 miles are $0.116/m³ and $0.089/m³/mile, respectively. We estimated the biomass (sludge) transportation cost per gallon of biodiesel, and observed the changes in these costs as a function of distance traveled and volume shipped. The outcomes of this study have the potential to help biofuel plants make better biomass transportation decisions, and consequently reduce the price of biodiesel significantly.     

Collective public-transport tickets and anticipated majority choice: A model of student tickets

In Germany, many universities have student tickets that are bargained for between student representatives and public transport companies, approved by referendum, and mandatory for all students. They allow the use of public transport at no additional cost. I analyze such a scenario in a theoretical model as an example of a flat-rate ticket for public transport which is implemented by majority decision. The mandatory character of the ticket reduces transaction costs like marketing and ticket inspection, reducing the ticket price and thus the students’ commuting expenses. However, there is a countervailing effect. Students face and rationally expect zero marginal monetary commuting costs, so that new students choose a place of residence which is relatively far from the university. This in turn raises the equilibrium ticket price. It may even be the case that students would be better off if such a ticket had never existed. Nonetheless, they always vote for it in referenda, because accepting the high price is optimal given their place of residence. After laying out the model, I analyze an optimal policy, which consists, for example, of subsidizing student dorms at an efficient distance to the city center.     

业主项目工程造价控制

随着我国国民经济的飞速发展,贷款修路,收费还贷的工程项目逐渐增多,工程造价的多少直接关系到还贷年限的长短,这一问题已经越来越显出其重要性。如何采取主动控制的手段合理确定和有效控制工程造价已成为工程管理的首要问题。文中从项目前期、招标阶段、施工阶段等过程对工程造价控制进行了论述。     

Determinants of the property damage costs of tanker accidents

This study investigates determinants of the vessel, oil cargo spillage, and other-property damage costs of tanker accidents. Tobit estimation of a three-equation recursive model suggests that, among types of tanker accidents, fire/explosion accidents incur the largest vessel damage costs, but the smallest oil cargo spillage costs. Alternatively, grounding accidents incur the smallest vessel damage costs, but the largest oil cargo spillage costs, reflecting the difficulty of controlling oil cargo spillage subsequent to such accidents. Also, oil cargo spillage costs are lower for US flag tanker accidents. A dollar of vessel damage cost increases other-property damage cost by $0.06, whereas a dollar of oil cargo spillage increases this cost by $1.55.     

Tradable credit schemes on networks with mixed equilibrium behaviors

This paper analyzes and designs tradable credit schemes on networks with two types of players, namely, a finite number of Cournot–Nash (CN) players and an infinite number of (infinitesimal) Wardrop-equilibrium (WE) players. We first show that there are nonnegative anonymous credit schemes that yield system optimum, when transaction costs are not considered. We then analyze how transaction costs would affect the trading and route-choice behaviors of both CN and WE players, and discuss the equilibrium conditions on the coupled credit market and transportation network in the presence of transaction costs. A variational inequality is formulated to describe the equilibrium and is subsequently applied to a numerical example to assess the impacts of transaction costs on a tradable credit system. As expected, transaction costs reduce the trading volume of credits and change their market price. They also change the way how players respond to credit charges in their route choices and cause efficiency losses to the credit schemes that are previously designed without considering transaction costs. With transaction costs, travel costs of WE players will likely increase while those of CN players may decrease due to their higher adaptability in routing strategies.     

The location of public logistic centers: an expanded capacity-limited fixed cost location-allocation modeling approach

The location problem considered in this paper concerns the optimal number, size, and location of public logistic centers. To solve this problem, a mathematical model is developed based on an expanded capacity-limited fixed cost location-allocation model of a network incorporating handling costs and the costs of the temporary storage of cargo in the logistic center. The effectiveness of the proposed approach is evaluated with a numerical example of locating public logistic centers of international importance in the Republic of Serbia, based on two scenarios regarding the future development of import cargo flows into the Republic to the year 2020.     

A demand model for recreational travel

A model is developed to describe and to predict the patterns of regional recreational travel. The model is designed in such a manner to allow its calibration and use without the need to conduct extensive travel surveys in a large region. To allow its use for prediction, the model is based on a causal structure and attempts to derive recreational travel demand from behavioural variables. The main hypothesis of the model is that the amount of recreational travel a recreation area attracts is affected by the accessibility of this area to points of demand potential and by its attractiveness relative to the recreation areas.

The calibration is founded on actual data on recreational travel to national forests in California, U.S.A. It is found in the calibration that accessibility to demand potential is the single most important determinant of recreational travel attraction. A simple relationship is derived to relate travel to each national forest to the relative accessibility of the forest. The model is calibrated and statistically validated.

It is suggested that when constructing travel demand models simplicity be sought, even at the risk of the loss of some explanatory power. In the calibration of such models statistical significant is more important than the ability to reproduce observed patterns.     

高速公路中间带优化设计方法研究

针对高速公路中间带面临的行车安全、路基水害等问题,提出了中间带优化设计方法,以达到减少中间带占用空间,增加路面有效宽度,提高行车安全性,避免水害,提高道路通行能力,降低全寿命周期成本的目标。     

改进的重置成本法确定二手车价值

在中国,二手车鉴定评估还缺乏科学统一的评估理论和方法。文中以重置成本法为依据,并对重置成本法进行了改进,阐述了如何利用改进的重置成本法来确定二手车价值,并进行了实例验证,证明了改进的重置成本法的有效性。