Optimal synthesis of function generation in steering linkages

This paper presents an approach to optimize planar mechanisms for function generation synthesis. It is applied to the design of different steering linkages used in road vehicles where the Ackermann condition is formulated as the objective function. Four different mechanisms are kinematically defined and synthesized in terms of the proposed method. Limitations of the size of the elements are also considered by means of inequality constraints. Solutions are presented as the difference between desired behaviour, established by Ackermann, and actual generated performance. The results show that the accuracy achieved by the proposed procedure is satisfactory for working conditions in this type of linkages.     

Benthic sediment composition and nutrient cycling in an Intermittently Closed and Open Lake Lagoon

Surfical sediments within Corunna Lake, a moderate size Intermittently Closed and Open Lake Lagoon (ICOLL), were examined for solid phase nutrient concentrations (TN, TP, TOC,) and solute exchange rates between the sediment and water column (O₂, NO₃–N, NH₄–N, FRP, and N₂). The surfical sediments in Corunna Lake contained high concentrations of TN (5 mg/g dry mass), total phosphorus (0.6 mg/g dry mass), and TOC (~ 5% dry mass). The carbon stable isotope ratio (δ¹³C) and TOC:TN ratios (δ¹³C ~ ? 24, TOC:TN ~ 11–14) demonstrated that the composition of the organic matter in the sediment was a mixture derived primarily of degraded planktonic matter. The close association between TP and Fe concentrations highlighted the potential role Fe plays in mediating Filterable Reactive Phosphorus (FRP) concentrations in the water column of Corunna Lake. In situ benthic chamber incubations were used to measure benthic fluxes. Solute exchange rates between the sediment and water column in Corunna Lake were similar to other reported studies (O₂ = ? 469 to ? 1765 µmol m^? 2 h^? 1, NH₄–N = 0.1–63 µmol m^? 2 h^? 1, NO₂/NO₃–N = 0 µmol m^? 2 h^? 1, FRP = ? 4–1.6 µmol m^? 2 h^? 1and N₂ = 12–356 µmol m^? 2 h^? 1). As more carbon was deposited and mineralized the efficiency of the bacterial population to denitrify nitrogen in the sediment decreases. The linkage between land use and benthic biogeochemistry was also explored. A dairy farm exists in the middle catchment of Corunna Lake, and the receiving bay sediment consistently demonstrated the highest oxygen consumption rates in winter and spring (? 1408 µmol m^? 2 h^? 1 in winter, ? 1691 µmol m^? 2 h^? 1 in spring) and lowest denitrification efficiencies during summer (~ 3%). Nitrate/nitrite fluxes were not observed during any of the chamber incubations, with the concentrations of nitrate/nitrite being below detection limits (< 10 μg/L). Seasonal changes influenced the rates of solute exchange between the sediment and water column. Critical measures of solute exchange for NH₄–N and biogenic N₂ indicated that seasonal temperature changes play a significant role in mediating the reaction rates of sedimentary based biogeochemical processes. Measurable FRP fluxes were small but greater in the benthic sediments which received higher carbon inputs. Sediments have a high capacity to adsorb P which is released as sediment oxygen demand increases as a result of increases in labile carbon loads.     

Modelling journey‐to‐work fuel consumption: a case study of Bayridge subdivision

Fuel consumption is calculated using a modelling procedure for automobiles travelling on three alternative street patterns designed for a subdivision in Kingston Township, Ontario. The modelling procedure is described. The results indicate that grid and solar superblock street patterns, compared to the existing street pattern, offer small fuel savings to a tripmaker in the portion of the work trip travelled in the subdivision.     

Cycle-simulation turbulence modelling of IC engines

Numerical simulations of IC engines are of high interest for automotive engineers worldwide. The simulation models should be as fast as possible, low-computational effort and predictive tool. The correct prediction of turbulence level inside the combustion chamber of spark ignition engines is the most important factor influencing to the engine working cycle. This paper presents a development of the k-ε turbulence model applied to the commercial cycle-simulation software with the high emphasis on the intake part. The validation was performed on two engine geometries with the variation of engine speed and load comparing the cycle-simulation results of the turbulent kinetic energy and in-cylinder temperature with 3-D CFD results. In order to apply the cycle-simulation turbulence model for the simulation of entire engine map, the parameterization model of turbulence constants was proposed. The parameterized turbulence model was optimized using NLPQL optimization algorithm where the single set of turbulence model parameters for each engine was found. A good agreement of the turbulent kinetic energy during the expansion was achieved when the turbulence affects the flame front propagation and combustion rate as well.     

A user‐resource planning framework for offshore recreational artificial reefs

Abstract

Artificial reefs have been used extensively in coastal waters to attract and enhance recreational fishery resources. In the United States, they have been traditionally built from “materials of opportunity”; using limited budgets. This paper explores some past planning philosophies and presents a recent artificial reef deployment case that demonstrates a lack of sensitivity to local and regional recreational demand. A systems framework is developed to guide future planning efforts in artificial reef development. The framework is intended to integrate previously fragmented knowledge and to demonstrate the interdisciplinary nature of artificial reef planning. Emphasis is given to advance planning, user dimensions, and the integral issue of reef access.     

Origin–destination table disaggregation using biproportional least squares estimation

This paper describes a group of techniques for disaggregating origin–destination tables for travel forecasting that makes explicit use of observed traffic on a network. Five models within the group are presented, each of which uses nonlinear least-squares estimation to obtain row and column factors for splitting trip totals from and to larger geographical areas into smaller ones. The techniques are philosophically similar to Fratar factoring, although the solution method is quite different. The techniques are tested on a full-sized network for Northfield, MN and are found to work effectively.     

Route choice of cyclists in Zurich

This paper presents the first route choice model for bicyclists estimated from a large sample of GPS observations and overcomes the limitations inherent in the generally employed stated preference approach. It employs an improved mode detection algorithm for GPS post-processing to determine trips made by bicycle, which are map matched to an enriched street network. The alternatives are generated as a random sample from an exhaustive, but constrained search. Accounting for the similarity between the alternatives with the path-size factor the MNL estimates show that the elasticity with regards to trip length is nearly four times larger than that with respect to the share of bike paths. The elasticity with respect to the product of length and maximum gradient of the route is small. No other variable describing the routes had an impact. The heterogeneity of the cyclists is captured through interaction terms formulated on their average behaviour.     

Efficiency and ecological characteristics of a VCR diesel engine

Compression ratio (CR) is a design parameter with highest influence on efficiency, emission and engine characteristics. In conventional internal combustion (IC) engines, the compression ratio is fixed and their performance is, therefore, a compromise between conflicting requirements. One fundamental problem is that drive units in the vehicles must successfully operate at variable speed and loads and in different ambient conditions. If a diesel engine has a fixed CR, a minimal value must be chosen that can achieve a reliable self-ignition when starting the engine in cold start conditions. In diesel engines, variable compression ratio (VCR) provides control of peak cylinder pressure, improves cold start ability and low load operation, enabling the multi-fuel capability, increase of fuel economy and reduction of emissions. By application of VCR and other mechanisms, the optimal regime fields are extended to the prime requirements: consumption, power, emission, noise, etc., and/or the possibility of the engine to operate with different fuels is extended. An experimental Diesel engine has been developed at the Faculty of Engineering, University of Kragujevac. The changes of CR are realized by changing the piston chamber diameter. Detailed engine tests were performed at the Laboratory for IC engines. Special attention has been given to decrease of fuel consumption and exhaust emissions. An optimal field of CR variation has been determined depending on the given objectives: minimal fuel consumption, minimal nitric oxides, and particulate matter emissions, etc.     

Finite element modeling of static tire enveloping characteristics

To investigate static tire enveloping characteristics, a three dimensional (3-D) finite element model is proposed. The vertical stiffness of the tire is studied on a flat surface with and without cleat. Tire rubber materials and cord layers are represented independently using “rebar” elements available in MSC Marc Mentat. Comparisons of numerical and experimental results are given to show the validity of the proposed model. It is shown that after a certain displacement, the results of the proposed model agree well with experimental results. In addition, the model results show that regardless of the type of the cleat placed under the rim center (hub center), all vertical force curves intersect after a certain displacement, which indicates typical static enveloping characteristics. Moreover, another typical characteristic of the radial tires that is unlike those of bias-ply constructions confirms that the contact patch does not expand laterally after a level vertical load is applied to the tire, which is directly related to fuel consumption and tire tread life.