Molecule conversion in recombining plasmas : the role of radical-surface interactions

The conversion of molecules proceeds commonly by activated chemical pro- cesses which require a high temperature, high pressure and often speci¯c catalytic surfaces. The use of a plasma introduces new degrees of control of the conversion processes. The feedstock gases are dissociated in the plasma, thereby eliminating one reason for activation. In particular at low pressure the association of plasma produced radicals occurs mainly at the walls of the reactor. In this thesis, the role of radical-surface interactions in a plasma reactor is investigated and details of these heterogeneous processes during exposure of the surfaces to an intense, recombining plasma are studied. To investigate the role of radical-surface interactions, the conversion of molecules in a plasma is studied in detail by means of mass spectrometry and a dedicated op- tical absorption spectroscopy system in two di®erent types of plasma reactors: an expanding thermal plasma (Eindhoven) and a microwave discharge (Greifswald). Although the reactors are fundamentally di®erent, the conversion of molecules on a global scale shows a remarkable resemblance. First of all radicals produced from feedstock gases containing N, H and O are mainly converted to N2, H2 and O2 (but also H2O). If the feedstock gases contain also C (e.g. CH4 or CO2) then CO is a major product. These results are independent of the nature of the feed- stock gases. Smaller fractions of other gases, like NO and NH3, have also been observed. Admixing O2 to plasmas created from a mixture of N2 and H2 results in both types of reactors in a signi¯cant decrease of the observed abundance of NH3. Instead, mainly H2O and NO are formed. We have studied the role of surface association in the formation of molecules by a detailed comparison of the measured composition of the studied plasmas with the results of a simulation that considers both homogeneous and heterogeneous interactions. In short, the conversion of molecules in low pressure, recombining plasma systems proceeds as follows. The injected gases are dissociated by the plasma and the plasma-produced radicals °ow through the volume towards the surfaces of the reactor where they adsorb to the surface, pick up a surface-adsorbed species or re°ect at the surface. Surface-adsorbed species also interact with each other, thereby producing new molecules that desorb from the surface. In the volume of the reactor, also gas phase interactions play a role and in°uence the composition of the plasma. The best agreement between calculations and measurements was found for low activation energies and desorption energies of the surface processes implemented in the simulation. A low surface coverage follows from the calculations. This can be interpreted as a layer of mobile species that contribute to surface association, on top of a passivating chemisorbed layer of radicals. By means of time-dependent dosing studies, the types of surface-adsorbed species during exposure of plasma produced radicals on stainless steel reactor walls are identi¯ed as: N, O, NO, H and NH2 in mixtures of nitrogen and oxygen or nitrogen and hydrogen. By comparing the results from the simulations with the measured composition of the plasma, it is shown in low pressure plasmas created from mixtures of N2 and O2 that the total rate of surface production is even in the same order as the rate of dissociation of the feedstock gases in the plasma. This indicates that surface association of plasma-produced radicals is a dominant process in the conversion of molecules in low pressure recombining plasma system

Item-score reliability:Estimation and evaluation

In psychology and education, tests are used to measure intelligence and school performance. Test scores are used to make decisions about individuals (who is admitted to a particular school level or a job?) and have impact on people’s lives as well as on schools and organizations. Thus, test scores must be reliable to guarantee that decisions based on test scores are correct. Reliability is the degree to which retesting a person provides the same result. In practice, re-testing the same persons to determine reliability is unrealistic, because memory and other unwanted effects will influence the test result. Estimation of a test score’s reliability therefore is based on the test results of a sample of people who took the test just once. This approach has produced several methods to estimate reliability of the test score. Methods for estimating the reliability of a test score all relate to a test consisting of multiple items (problems to be solved, questions to be answered). However, individual items also must have high reliability, and thus it is important to assess the reliability of a single item, that is, the item-score reliability. So far, items were assessed using indices that address aspects of item quality other than reliability, but methods to assess item-score reliability were hardly available and thus had to be developed and their performance evaluated. This was the topic of this dissertation. In this dissertation, methods for estimating item-score reliability were developed and the usability of these methods was evaluated. First, reliability methods based on test scores were used as a basis for developing methods for estimating item-score reliability. These methods were evaluated in controlled studies using simulated data. Three promising methods resulted. In a second study, these three item-score reliability methods were used to estimate the item-score reliability in several empirical-data sets. The resulting values were compared to values of item indices assessing other aspects of item quality. The relation between the three item-score reliability methods and the other item indices was investigated in a third study using simulated data. In a final study, the usability of item-score reliability for selecting or rejecting items based on their contribution to test-score reliability was investigated. The studies in this dissertation show that item-score reliability methods provide insight into the quality of an item and help to decide whether an item should be included in the test. Also, the relationship between item-score reliability and other aspects of item quality is investigated. Our methods may contribute to the improvement of psychological and educational tests

Mitigation and Compensation Measures under the EU Habitats Directive in Selected Member States

This article aims at establishing how national courts interpret the concepts of mitigation and compensation measures under Article 6 of the Habitats Directive. Based on a comparative method of legal research, we focus on the implementation of Articles 6(3) and 6(4) of the Habitats Directive, as interpreted by the Court of Justice of the European Union in the Sweetman, Briels and Orleans cases, and its application in the courts of six Member States, i.e. France, Germany, the UK, the Netherlands, Italy and Bulgaria. Our study highlights national courts tendency to interpret the Habitats Directive and related national law so as to cover matters which have not explicitly been dealt with by the CJEU without asking for preliminary rulings. In each legal order, this lack of preliminary references comported a wrongful interpretation of Article 6(3) of the Directive. This finding shows that the lack of preliminary references affected the legal effectiveness of Article 6 HD

The Alignment of IT and Business Strategy at ROC Leeuwenborgh

ICT Lyceum ROC Leeuwenborgh tends to have IT strategic plan as a guideline to aligned between IT and business strategy. The main goal of this research is to make a recommendations for the new IT strategy implementation as a part of EA that can support the business goals. In order to create the recommendation, Strategic Information System Planning with Ward and Peppard method has been used. The perspective contains 3 models analysis: Porter’s Five Forces, McFarlan Strategic Grid, and Strategic Alignment. Afterward, the strengths, weaknesses, opportunities, and threats were put into a TOWS matrix in order to create the strategies options. Strategies options were being used to create the recommendations of information technology in hardware and software