Prediction of in-use emissions of heavy-duty diesel vehicles from engine testing

A model of a heavy-duty vehicle driveline with automatic transmission has been developed for estimating engine speed and load from vehicle speed. The model has been validated using emissions tests conducted on three diesel vehicles on a chassis dynamometer and then on the engines removed from the vehicles tested on an engine dynamometer. Nitrogen oxide (NOx) emissions were proportional to work done by the engine. For two of the engines, the NOx/horsepower(HP) ratio was the same on the engine and on the chassis dynamometer tests. For the third engine NOx/HP was significantly higher from the chassis test, possibly due to the use of dual engine maps. The engine certification test generated consistently less particulate matter emissions on a gram per brake horsepower-hour basis than the Heavy Duty Transient and Central Business District chassis cycles. A good linear correlation (r2 = 0.97 and 0.91) was found between rates of HP increase integrated over the test cycle and PM emissions for both the chassis and the engine tests for two of the vehicles. The model also shows how small changes in vehicle speeds can lead to a doubling of load on the engine. Additionally, the model showed that it is impossible to drive a vehicle cycle equivalent to the heavy-duty engine federal test procedure on these vehicles.     

Why Napster matters to writing: Filesharing as a new ethic of digital delivery

This article discusses the Napster phenomenon and its cultural significance, traces some of the threads of the current “copyright crisis,” and connects these cultural and legal dynamics to show how the current filesharing context of digital environments pertains to issues affecting writing teachers. The article (1) urges writing teachers to view the Napster moment—and the writing practice at the center of it, filesharing—in terms of the rhetorical and economic dynamics of digital publishing and in the context of public battles about copyright and intellectual property and (2) argues that digital filesharing forms the basis for an emergent ethic of digital delivery, an ethic that should lead composition teachers to rethink pedagogical approaches and to revise plagiarism policies to recognize the value of filesharing and to acknowledge Fair Use as an ethic for digital composition.     

Discrete Working Time Choice in an Applied General Equilibrium Model

We present a model that integrates the discrete working time choice of heterogenous households into a general equilibrium setting where wages are determined by sectoral bargaining between firms and trade unions. The model is calibrated to German micro and macro data. We then use it to analyse a stylised policy reform designed to stimulate labour supply. JEL Code: D58, J22, J51 An erratum to this article can be found at     

Conductometric detection of anions of weak acids in chemically suppressed ion chromatography: critical point concentrations

Previously we demonstrated that the conductometric determination of anions of weak acids in chemically suppressed ion chromatography could be enhanced, by conversion of the acid to a conjugate salt, if the anion was present above what we termed the critical point concentration (CPC). In this paper we have developed a simple theoretical model for the calculation of CPCs for weak acid/conjugate salt pairs. The CPC was found to be dependent on the acid ionization constant K(a) and the molar ionic conductivities (MICs) of the ions present. For monovalent anions with a MIC in the common range 25-75 S cm(2) mol(-)(1), with sodium or potassium as cations, the CPCs could be estimated from the expression pC ≈ pK(a) - 1, where pC = -log CPC. For formate, benzoate, and acetate, excellent agreement was found between the calculated and experimental CPCs, with a mean deviation of 0.05 mM. For fluoride, the calculated and experimental CPCs were 7.4 and 9.2 mM, respectively. Experimental CPCs could not be determined for other anions as their calculated CPCs were below the detection limits of the IC system. The simple theoretical model could also be used to estimate the expected conductivity enhancement for the conversion of weak acid to a particular conjugate salt. The effects of detector linearity and dispersion in the IC system on the use of CPCs are also discussed.     

Design of an integrating cavity absorption meter

The design of integrating cavity absorption meters of general geometry is analyzed for cases in which the incident illumination of the cavity is spatially uniform and isotropic, such as the meter of Fry et al. [Appl. Opt. 31, 2055 (1992)]. The analysis by Kirk [Appl. Opt. 34, 4397 (1995)] for the probability of photon survival in a spherical meter is extended to general geometries. An estimate of the effect of the shape of the cavity on the estimated absorption coefficient is given.     

Ocean inherent optical property determination from in-water light field measurements

An algorithm is described and evaluated for determining the absorption and backscattering coefficients a(z) and bb(z) from measurements of the nadir-viewing radiance Lu(z) and downward irradiance Ed(z). The method, derived from radiative transfer theory, is similar to a previously proposed one for Eu(z) and Ed(z)and both methods are demonstrated with numerical simulations and field data. Numerical simulations and a sensitivity analysis show that good estimates of a(z) and bb(z) can be obtained if the assumed scattering phase function is approximately correct. In an experiment in Long Island Sound, estimates of a(z) derived with these methods agreed well with those obtained from an in situ reflecting tube instrument.     

Evaluation of functions on microcomputers: square root

This paper treats the evaluation of one of the elementary functions on short wordlength computers. The setting is a binary fixed point short wordlength (8–16 bits) machine where the intent is to suggest improvements in ROM- or microcode-based software which include the square root function as part of a more general mathematical software library or for special computation in real-time applications. This paper focuses on the evaluation of square roots and features a careful treatment of Newton's method with linear initialization. Comparisons with other popular algorithms are made based on storage requirements, speed, and accuracy, with some indication of the effect that special hardware features have on the performance of these routines.     

A critique of inverse solutions to slab geometry transport problems

An inverse transport problem requires determination of the angular scattering and absorption coefficients of the medium using measurements of the intensity. Methods for solving such a problem for monoenergetic transport in a thick homogeneous (i.e. multiple-scattering) slab medium are critiqued. The methods include those that require local measurement of the intensity inside the slab plus remote measurement of the angular distributions entering and leaving (the local-&-remote methods) and those (remote methods) that require only the surface angular distributions. The possible use of these methods to determine the properties of a multi-layer slab medium is also examined.     

Need for recovery from work: evaluating short-term effects of working hours,patterns and schedules

In this paper working hours, patterns and work schedules of employees were evaluated in terms of need for recovery from work. Self-administered questionnaire data from employees of the Maastricht Cohort Study on Fatigue at Work (n = 12,095) were used. Poisson regression analyses and multivariate logistic regression analyses revealed that higher working hours a day and working hours a week generally went together with more need for recovery from work. Overtime work was particularly associated with higher need for recovery from work in both genders. Both male and female three-shift or irregular shift workers had higher odds of elevated need for recovery compared to day workers. When additionally controlling for work-related factors, need for recovery levels among shift workers substantially lowered. This study clearly showed that working hours and schedules are associated with need for recovery from work, with different associations for men and women. Especially the associations between work schedules and need for recovery from work were very interrelated with other work-related factors. Future studies could further investigate the possibility that shift work might function as a proxy of other work-related factors that explain the different levels in need for recovery from work, or that job demands are perceived higher among shift workers and may therefore lead to more need for recovery from work.