Introducing a hyperbolic vortex into a showerhead is a possibility to achieve higher spray velocities for a given discharge without reducing the nozzle diameter. Due to the introduction of air bubbles into the water by the vortex, the spray is pushed from a transition (dripping faucet) regime into a jetting regime, which results in higher droplet and jet velocities using the same nozzle diameter and throughput. The same droplet and jet diameters were realized compared to a showerhead without a vortex. Assuming that the satisfaction of a shower experience is largely dependent on the droplet size and velocity, the implementation of a vortex in the showerhead could provide the same shower experience with 14% less water consumption compared to the normal showerhead. A full optical and physical analysis was presented, and the important chemical parameters were investigated.
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Recent and ongoing curriculum innovations in Dutch secondary chemistry education have led to questions about which concepts should be central in the programme and which contexts should be used to embed these concepts into. Another important question is in the discussions about these innovations is: how do students learn chemistry? This thesis examines the relations between students' metacognitive beliefs, their learning outcomes, and the learning activities they conduct in the domain of chemistry. In studying these relations, a useful framework is provided bij Novak's educational theory on 'meaningful learning' as is described in chapter 2. In chapter 3, the development of an instrument for assessing students' metacognitive beliefs regarding chemistry is described. More specifically, this instrument, a questionnaire, consists of items that can be used to determine the nature of students' epistemological beliefs, learning conceptions, and goal orientations concerning chemistry. Using this instrument, it was found that the students' aforementioned metacognitive beliefs were highly interrelated. By means of the data produced in this study, an improved version of the instrument was constructed. We used this version of the instrument in a follow-up study and identified a set of items to assess a student's 'competence mindedness'. 'Competence mindedness' is defined as the extent to which students are oriented towards coming to understand subject matter in the chemical domain. This orientation is for instance inferred from students' beliefs about chemistry as a coherent body of knowledge and about chemistry learning as a process in which knowledge is actively constructed. We describe a student's score on this scale as the extent to which he is oriented towards developing chemical competence, or, in short, the student's 'competence mindedness'. As an indicator of students' chemical competence we used the so-called 'macro-micro concept'. The macro-micro concept consists of the ability to use the macro perspective (focusing on chemical phenomena on a substance level) and micro perspective on chemistry (focusing on the structure and behavior of subatomic particles) interchangeably. Although the macro-micro concept is considered to be a central chemical competence by many experts in the field of chemistry education, the concept itself is not mentioned explicitely in any Dutch chemistry textbook used in secondary education. Using the final version of the instrument described in chapter 3, relations between the competence mindedness of students and a central chemical competency were assessed in chapter 4. Consequently, an explorative study was conducted in which a small number of chemistry teachers was questioned on the extent to which they paid attention to the macro-micro concept in their own teaching. Five out of nine teachers interviewed, held the opinion that the macro-micro concept should be a part of chemistry teaching and consequently dedicated time in class to this concept. The other teachers that were interviewed, did not mention the macro-micro concept as a central chemical concept in the interviews. In another study, students' use of the macro-micro concept when answering regular chemistry test questions, was examined. From this study, it can be concluded that there are large differences in the students' use of this concept. However, from answers given by the students involved, it can be concluded that they use the macro-micro concept. Following from the last two studies mentioned, two more studies were conducted that focused on the use of the macro-micro concept by students. In particular we were interested in the way students use this concept differently than is to be expected from the sequencing of learning contents in chemistry textbooks. More specifically, we conducted two studies to determine if students' competence mindedness and the way they use the macro-micro concept (i.e. starting from the micro aspect or not) are related. In the first, small-scale, study, we concluded that senior students that are more competence minded, more often take the micro aspect of chemistry as a starting point when relating the micro and macro aspects of chemistry. In a follow-up study, a standardized instrument was used to assess students' use of the macro-micro concept. This instrument made it possible to include a larger sample of students in the study. This study confirmed the results found in the small-scale study: more competence minded students were found to prefer relations between the macro and micro aspects of chemistry that started from the micro aspect. Chapter 5 consists of several studies concerning students' notions about how the chemical domain can be described: their chemical domain beliefs. The development of these notions are considered an important indicator of chemical competence. Relations between students' competence mindedness and aspects of their chemical domain beliefs were examined through a repertory test procedure. More specifically, the students involved in this study were asked to compare the subject of chemistry with several other subjects. Thereby, data were gathered on constructs these students' used to describe the subject of chemistry and how they contrasted with the other subjects or resembled them. In another study, relations between students' chemical domain beliefs and the extent to which these students are competence minded were examined. The results show a number of relations between students' competence mindedness and selections of their chemical domain beliefs: in general, more competence minded students more often use concepts like 'chemistry as a science', 'properties of substances', and 'chemical reactions' to typify chemistry. Having found indications that students' competence mindedness regarding chemistry is related to their learning outcomes, the question arises how students' competence mindedness can be enhanced. Moreover, relations between students' competence mindedness and the learning strategies they deploy, have not been taken into consideration up to this point. In chapter 6, a learning environment was redesigned in the form of a student study guide, that is used as a supplement to the chemistry textbook students were used working with. The main purpose of the study guide was to change the type of learning activities students use. The two quasi-experimental studies in which the study guide was used as an intervention, did not lead to significant changes in students' learning activities. However, relations were found between students' learning activities and the extent to which students were competence minded. We conclude therefore, that the learning strategies used by the students involved in the study are in particular a consequence of their metacognitive beliefs, i.e. their competence mindedness, and not of the learning environment concerned.
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With a market demand for low cost, easy to produce, flexible and portable applications in healthcare, energy, biomedical or electronics markets, large research programs are initiated to develop new technologies to provide this demand with new innovative ideas. One of these fast developing technologies is organic printed electronics. As the term printed electronics implies, functional materials are printed via, e.g. inkjet, flexo or gravure printing techniques, on to a substrate material. Applications are, among others, organic light emitting diodes (OLED), sensors and Lab-on-a-chip devices. For all these applications, in some way, the interaction of fluids with the substrate is of great importance. The most used substrate materials for these low-cost devices are (coated) paper or plastic. Plastic substrates have a relatively low surface energy which frequently leads to poor wetting and/or poor adhesion of the fluids on the substrates during printing and/ or post-processing. Plasma technology has had a long history in treating materials in order to improve wetting or promote adhesion. The µPlasma patterning tool described in this thesis combines a digital inkjet printing platform with an atmospheric dielectric barrier discharge plasma tool. Thus enabling selective and local plasma treatment, at atmospheric pressure, of substrates without the use of any masking materials. In this thesis, we show that dependent on the gas composition the substrate surface can either be functionalized, thus increasing its surface energy, or material can be deposited on the surface, lowering its surface energy. Through XPS and ATR-FTIR analysis of the treated (polymer) substrate surfaces, chemical modification of the surface structure was confirmed. The chemical modification and wetting properties of the treated substrates remained present for at least one month after storage. Localized changes in wettability through µPlasma patterning were obtained with a resolution of 300µm. Next to the control of wettability of an ink on a substrate in printed electronics is the interaction of ink droplets with themselves of importance. In printing applications, coalescence of droplets is standard practice as consecutive droplets are printed onto, or close to each other. Understanding the behaviour of these droplets upon coalescence is therefore important, especially when the ink droplets are of different composition and/or volume. For droplets of equal volume, it was found that dye transport across the coalescence bridge could be fully described by diffusion only. This is as expected, as due to the droplet symmetry on either side of the bridge, the convective flows towards the bridge are of equal size but opposite in direction. For droplets of unequal volume, the symmetry across the bridge is no longer present. Experimental analysis of these merging droplets show that in the early stages of coalescence a convective flow from the small to large droplet is present. Also, a smaller convective flow of shorter duration from the large into the small droplet was identified. The origin of this flow might be due to the presence of vortices along the interface of the bridge, due to the strong transverse flow to open the bridge. To conclude, three potential applications were showcased. In the first application we used µPlasma patterning to create hydrophilic patterns on hydrophobic dodecyl-trichlorosilane (DTS) covered glass. Capillaries for a Lab-on-a-chip device were successfully created by placing two µPlasma patterned glass slides on top of each other separated by scotch tape. In the second application we showcased the production of a RFID tag via inkjet printing. Functional RFID-tags on paper were created via inkjet printing of silver nanoparticle ink connected to an integrated circuit. The optimal operating frequency of the produced tags is in the range of 860-865 MHz, making them usable for the European market, although the small working range of 1 m needs further improvement. Lastly, we showed the production of a chemresistor based gas sensor. In house synthesised polyemeraldine salt (PANi) was coated by hand on top of inkjet printed silver electrodes. The sensor proved to be equally sensitive to ethanol and water vapour, reducing its selectivity in detecting changes in gas composition.
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Metaphors are at the basis of our understanding of reality. Using the theory of metaphor developed by Lakoff and Johnson (1980, 1999) this paper analyses common metaphors used in the intellectual capital and knowledge management literatures. An analysis of key works by Davenport & Prusak (2000), Nonaka & Takeuchi (1995), and Stewart (1991) suggests that at least 95 percent of all statements about either knowledge or intellectual capital are based on metaphors. The paper analyses the two metaphors that form the basis for the concept of intellectual capital: ‘Knowledge as a Resource’ and ‘Knowledge as Capital’, both of which derive their foundations from the industrial age. The paper goes into some of the implications of these findings for the theory and practice of intellectual capital. Common metaphors used in conceptualising abstract phenomena in traditional management practices unconsciously reinforce the established social order. The paper concludes by asking whether we need new metaphors to better understand the mechanisms of the knowledge economy, hence allowing us to potentially change some of the more negative structural features of contemporary society.
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Saturated hydraulic conductivity (Ks) of the filler layer in grassed swales are varying in the changing environment. In most of the hydrological models, Ks is assumed as constant or decrease with a clogging factor. However, the Ks measured on site cannot be the input of the hydrological model directly. Therefore, in this study, an Ensemble Kalman Filter (EnKF) based approach was carried out to estimate the Ks of the whole systems in two monitored grassed swales at Enschede and Utrecht, the Netherlands. The relationship between Ks and possible influencing factors (antecedent dry period, temperature, rainfall, rainfall duration, total rainfall and seasonal factors) were studied and a Multivariate nonlinear function was established to optimize the hydrological model. The results revealed that the EnKF method was satisfying in the Ks estimation, which showed a notable decrease after long-term operation, but revealed a recovery in summer and winter. After the addition of Multivariate nonlinear function of the Ks into hydrological model, 63.8% of the predicted results were optimized among the validation events, and compared with constant Ks. A sensitivity analysis revealed that the effect of each influencing factors on the Ks varies depending on the type of grassed swale. However, these findings require further investigation and data support.
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Innovation is not what it was in the 20th century; the classic century of R & D based innovation. The nature of innovation is changing, only in part because different technologies dominate innovation. This paper identifies three main societal trends that are of major importance for strategic management of innovation in industry and for government industrial- and technology policies. These trends are: - Growing complexity - Globalisation - Citizen participation As a result, innovation strategy and technology policies cannot be determined by ad hoc technology push and market pull factors popping up. Strategic planning, not just of products and technologies but also of sites and alliances becomes increasingly important. Transparency and stakeholder dialogue require new competencies of the technology manager.
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Een fles rode wijn per dag drinken is ongezond, maar een glas per dag reduceert mogelijk de kans op hartkwalen. Dit is een voorbeeld van ‘hormese’: het verschijnsel dat een agens dat in grote hoeveelheden schadelijk is, bij lage doses juist gezond is. Iets vergelijkbaars geldt voor zonlicht: lage doses worden geassocieerd met positieve gezondseffecten, hoge doses met verbranden en een hogere kans op huidkanker. Er zijn onderzoekers die zich op het omstreden standpunt stellen dat ook ioniserende straling hormetische eigenschappen heeft. In dit artikel gaan we nader in op de verschillende standpunten omtrent lage-dosiseffecten, de argumenten voor en tegen hormese en de consequenties van recente inzichten.
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Fouling plays a major role in the Dairy industry. Five criteria: defined flow, no circulation, real factory product, defined product temperature and defined wall temperature, are used to review articles on this topic published between 2003 and 2020. To show the effect of those criteria in experiments, a simulation model is developed. For a good experimental design to measure fouling, the use of a dairy product in a tubular heater with a known developed flow is advised. The temperature-time history of the product and the wall temperature of the heater should be recorded. Circulation of a product will increase the fouling and decrease the flow. Although none of the reviewed articles complied to all criteria, 71% of the reviewed articles met at least two criteria. If not all criteria are met, the results are of less use for the application for process lines on industrial scale. A simulated computer model can be helpful.
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Due to fast and unpredictable developments, professional education is challenged with being responsive, which demands a rethinking of conventional curriculum development approaches. Yet, literature on curriculum development falls short in terms of recognising how to react rapidly and adequately to these new developments. This study focuses on curriculum development initiatives at the school level in a Dutch university of applied sciences. Open interviews were held with 29 curriculum developers to explore how they define and give substance to developing curricula for new, changing or unpredictable professions. These 29 participants were involved in seven curriculum development trajectories. Four themes were detected: (1) curriculum developers are in favour of open, flexible and authentic curricula; (2) the context in which the curriculum development takes place and the different roles and responsibilities of curriculum developers are challenging; (3) curriculum developers feel insufficiently equipped to carry out their tasks; and (4) involving stakeholders is necessary but results in a “viscous” social–political process. Responsive curriculum development requires a great deal of flexibility and adaptability from curriculum developers. Yet, in our study, “institutional concrete” is found to severely hinder responsive curriculum development processes. To be responsive, such processes need to be supported and institutional barriers need to be removed.
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Many students in secondary schools consider the sciences difficult and unattractive. This applies to physics in particular, a subject in which students attempt to learn and understand numerous theoretical concepts, often without much success. A case in point is the understanding of the concepts current, voltage and resistance in simple electric circuits. In response to these problems, reform initiatives in education strive for a change of the classroom culture, putting emphasis on more authentic contexts and student activities containing elements of inquiry. The challenge then becomes choosing and combining these elements in such a manner that they foster an understanding of theoretical concepts. In this article we reflect on data collected and analyzed from a series of 12 grade 9 physics lessons on simple electric circuits. Drawing from a theoretical framework based on individual (conceptual change based) and socio-cultural views on learning, instruction was designed addressing known conceptual problems and attempting to create a physics (research) culture in the classroom. As the success of the lessons was limited, the focus of the study became to understand which inherent characteristics of inquiry based instruction complicate the process of constructing conceptual understanding. From the analysis of the data collected during the enactment of the lessons three tensions emerged: the tension between open inquiry and student guidance, the tension between students developing their own ideas and getting to know accepted scientific theories, and the tension between fostering scientific interest as part of a scientific research culture and the task oriented school culture. An outlook will be given on the implications for science lessons.
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