Analysis and verification of an automatic document feeder

Modern copying machines are versatile and complex systems in which embedded software plays an essential role. The progress towards faster and more stable machines that can satisfy ever growing customers' needs, places strict requirements on the efficiency and quality of such software. In order to meet these requirements, the software should be well-designed and free of errors. Using modern formal verification techniques, software designs can be checked for errors and deadlocks so that their quality can be assessed and improved at an early stage of the development process. In this paper, we analyze the embedded software of an Automatic Document Feeder (ADF). ADFs are important components of copier machines. The ADF studied here is a prototype developed by Océ-Technologies B.V., a company that develops professional printing systems. We construct a model of the ADF in µcrl, a process algebra-based specification language, and express the system's requirements in the modal µ-calculus. Next, we use the µcrl and Cadp tool sets to check whether the system meets its requirements. This analysis reveals important errors in the ADF and we propose solutions to these problems. Also, we show that some requirements that engineers assumed to be valid, are too strict. We present slightly weaker versions of these requirements and show that these do hold. In this sense, in addition to finding errors in the ADF, our analysis also led to a better understanding of the behaviour the system

Expanding School Enrollment by Subsidizing Private Schools: Lessons from Bogotá

Many countries use tax revenues to subsidize private schools. Whether these policies meet social objectives depends, in part, on the relative quality of education provided by the two types of schools. We use data on elementary school students and their teachers in Bogotá, Colombia to examine difference in resource mixes and differences in the relative effectiveness of public and private schools. We find that, on average, the schools in the two sectors are equally effective. However, they produce education using very different resource combinations. Moreover, there are large differences in the effectiveness of schools in both sectors, especially in the private sector. The results of our analysis shed light on the quantity-quality tradeoff that governments in many developing countries face in deciding how to use scarce educational resources.

Fuel and combustion stratification study of Partially Premixed Combustion

Relatively high levels of stratification is one of the main advantages of Partially Premixed Combustion (PPC) over the Homogeneous Charge Compression Ignition (HCCI) concept. Fuel stratification smoothens heat releaseand improves controllability of this kind of combustion. However, the lack of a clear definition of “fuel and combustion stratifications” is obvious in literature. Hence, it is difficult to compare stratification levels of different PPC strategies or other combustion concepts. The main objective of this study is to define the fuel and combustion stratifications based on the fuel tracer LIF and OH* chemiluminescence images, respectively. A light duty optical engine has been used to perform the measurements. Four experimental points are evaluated, with injection timings in both the homogeneous and the stratified regimes. Twodimensional Fourier transforms of fuel distribution and chemiluminescence images provide the range of spatial frequencies in these images. This method gives the opportunity to separate a specific range of frequencies related to fuel and combustion stratification. The signal energy content in this range is used to define the stratification, using an appropriate normalization procedure. The results indicate that this new definition is a promising method to compare the level of stratification between different experiments

Rabbits (<i>Oryctolagus cuniculus</i> L.) in coastal dune grasslands

We describe a field experiment for examining the impact of wild rabbits (Oryctolagus cuniculus L.) on the vegetation in two Flemish coastal dune grasslands. When numerous, rabbits had a major impact on the vegetation. This impact can be considered positive in the case of the studied grasslands, as evidenced by a decreasing abundance by dominant grass species and a declining species richness. The decrease of the number of rabbits, due to VHS, may hence negatively affect dune grassland species richness. Introducing large herbivores can be part of the solution for preserving the dune grasslands, and this introduction may even have positive effects on rabbit populations through feeding facilitation

A Numerical Study of Fuel Stratification, Heat Transfer Loss, Combustion, and Emissions Characteristics of a Heavy- Duty RCCI Engine Fueled by E85/Diesel

Reactivity-controlled compression ignition is a new advanced combustion strategy developed to reach cleaner and more efficient combustion by controlling fuel stratification inside the engine cylin-der and reducing heat loss. While its potential to produce high efficiency and low emissions and to reach higher loads than other Low-Temperature Combustion strategies (LTC) has been confirmed numerous times, its operating range is still limited to moderate loads. One potential solution to in-crease the operating range is using E85 fuel as the premixed fuel due to the potential of providing a longer combustion duration. This work will focus on developing a computational fluid dynamics (CFD) model for a reactivity-controlled compression ignition (RCCI) engine fueled by E85/diesel with a double step piston bowl geometry. The model is used to investigate the effects of four differ-ent design parameters, namely injection timing, boost pressure, initial temperature, and spray in-cluded angle, to identify their impact on all crucial parameters describing combustion i.e. the strati-fication level, heat loss, and emissions characteristics. It has been found that the start of injection affects the fuel stratification levels inside the cylinder, with the optimum location for efficiency lo-cated in the moderate stratified region. The boost pressure mainly influences the mean gas tem-perature, the start of combustion, combustion duration, and the recession time of the Heat Release Rate (HRR) curve. It is found that the boost pressure does not have an influence on the heat loss of the engine and the heat loss is more correlated to flame temperature than the average tempera-ture. It is also proven that the boost pressure could assist in the suppression of NOx, but when the intake pressure is too high, the thermal efficiency drops. Furthermore, the results show that the ini-tial temperature is preferred to be as low as possible but sufficiently high enough to burn all the in-troduced fuel. Intake temperature alters the HRR shape and combustion duration significantly. Last-ly, it is found that the combination of the spray included angle and piston bowl geometry can sub-stantially determine the way the flame is formed and its location. The study on the effect of spray angle provides essential insights on the origin of unburned hydrocarbon emission, HRR shape, and heat loss