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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This paper presents a mixed methods study in which 77 students and 3 teachers took part, that investigated the practice of Learning by Design (LBD). The study is part of a series of studies, funded by the Netherlands Organisation for Scientific Research (NWO), that aims to improve student learning, teaching skills and teacher training. LBD uses the context of design challenges to learn, among other things, science. Previous research showed that this approach to subject integration is quite successful but provides little profit regarding scientific concept learning. Perhaps, when the process of concept learning is better understood, LBD is a suitable method for integration. Through pre- and post-exams we measured, like others, a medium gain in the mastery of scientific concepts. Qualitative data revealed important focus-related issues that impede concept learning. As a result, mainly implicit learning of loose facts and incomplete concepts occurs. More transparency of the learning situation and a stronger focus on underlying concepts should make concept learning more explicit and coherent.
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The Smart Current Limiter is a switching DC to DC converter that provides a digitally pre-set input current control for inrush limiting and power management. Being able to digitally adjust the current level in combination with external feedback can be used for control systems like temperature control in high power DC appliances. Traditionally inrush current limiting is done using a passive resistance whose resistance changes depending on the current level. Bypassing this inrush limiting resister with a Mosfet improves efficiency and controllability, but footprint and losses remain large. A switched current mode controlled inrush limiter can limit inrush currents and even control the amount of current passing to the application. This enables power management and inrush current limitation in a single device. To reduce footprint and costs a balance between losses and cost-price on one side and electromagnetic interference on the other side is sought and an optimum switching frequency is chosen. To reduce cost and copper usage, switching happens on a high frequency of 300kHz. This increases the switching losses but greatly reduces the inductor size and cost compared to switching supplies running on lower frequencies. Additional filter circuits like snubbers are necessary to keep the control signals and therefore the output current stable.
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The application of DC grids is gaining more attention in office applications. Especially since powering an office desk would not require a high power connection to the main AC grid but could be made sustainable using solar power and battery storage. This would result in fewer converters and further advanced grid utilization. In this paper, a sustainable desk power application is described that can be used for powering typical office appliances such as computers, lighting, and telephones. The desk will be powered by a solar panel and has a battery for energy storage. The applied DC grid includes droop control for power management and can either operate stand-alone or connected to other DC-desks to create a meshed-grid system. A dynamic DC nano-grid is made using multiple self-developed half-bridge circuit boards controlled by microcontrollers. This grid is monitored and controlled using a lightweight network protocol, allowing for online integration. Droop control is used to create dynamic power management, allowing automated control for power consumption and production. Digital control is used to regulate the power flow, and drive other applications, including batteries and solar panels. The practical demonstrative setup is a small-sized desktop with applications built into it, such as a lamp, wireless charging pad, and laptop charge point for devices up to 45W. User control is added in the form of an interactive remote wireless touch panel and power consumption is monitored and stored in the cloud. The paper includes a description of technical implementation as well as power consumption measurements.
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Learning by Design (LBD) is a project-based inquiry approach for interdisciplinary teaching that uses design contexts to learn skills and conceptual knowledge. Research around the year 2000 showed that LBD students achieved high skill performances but disappointing conceptual learning gains. A series of exploratory studies, previous to the study in this paper, indicated how to enhance concept learning. Small-scale tested modifications, based on explicit teaching and scaffolding, were promising and revealed improved conceptual learning gains. The pretest-posttest design study discussed in this paper confirms this improvement quantitatively by comparing the conceptual learning gains for students exposed to the modified approach (n = 110) and traditional approach (n = 77). Further modifications, which resulted in a remodified approach tested with 127 students, show a further improvement through reduced fragmentation of the task and addressed science. Overall, the remodified approach (FITS model: Focus - Investigation - Technological design - Synergy) enriches technology education by stimulating an empirical and conceptual way of creating design solutions.
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Electrohydrodynamic atomization (EHDA) is a technique which uses the influence of strong electric fields to manipulate the break-up of a liquid, pumped through a capillary nozzle, into droplets. In this work, an extended description of a specific high flow EHDA mode, known as the simple-jet mode, is presented. In it, a review of different works published about the mode is presented as well as results about the droplet population generated with varicose and whipping break-up using water as the atomized liquid. Additionally, experiments were conducted to investigate whether such atomization method could be used to improve the efficiency of droplet inair evaporation, using a single effect evaporation chamber coupled with a EHDA multinozzle system functioning as a shower head. The liquid used in these experiments was a solution of water and NaCl (35 g L−1) to simulate sea water average concentrations. The results have shown that, the manipulation of the droplet diameter, droplet size distribution and spray angle, provided by EHDA, could improve the droplet evaporation efficiency by up to 40% when combinedwith, e.g. forced convection and higher inlet temperatures.
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This paper presents a mixed methods study in which 21 first-year student teachers took part that investigated learning outcomes of a modified learning by design task. The study is part of a series of studies that aims to improve student learning, teaching skills and teacher training. Design-based science challenges are reasonably successful project-based approaches for breaking down the boundaries between traditional school subjects. Previous learning outcomes of the extensively studied Learning by Design (LBD) approach demonstrated a strong positive effect on students’ skills. However, compared to traditional classroom settings, LBD provided little or no profit on (scientific) concept learning. For this, according to two preliminary studies, a lack of explicit teaching and scaffolding strategies, both strongly teacher-dependent, bears a share of responsibility. The results of this third study indicate that more emphasis on these strategies indeed strengthens concept learning without reducing positive effects on skill performance.
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Neighborhood image processing operations on Field Programmable Gate Array (FPGA) are considered as memory intensive operations. A large memory bandwidth is required to transfer the required pixel data from external memory to the processing unit. On-chip image buffers are employed to reduce this data transfer rate. Conventional image buffers, implemented either by using FPGA logic resources or embedded memories are resource inefficient. They exhaust the limited FPGA resources quickly. Consequently, hardware implementation of neighborhood operations becomes expensive, and integrating them in resource constrained devices becomes unfeasible. This paper presents a resource efficient FPGA based on-chip buffer architecture. The proposed architecture utilizes full capacity of a single Xilinx BlockRAM (BRAM36 primitive) for storing multiple rows of input image. To get multiple pixels/clock in a user defined scan order, an efficient duty-cycle based memory accessing technique is coupled with a customized addressing circuitry. This accessing technique exploits switching capabilities of BRAM to read 4 pixels in a single clock cycle without degrading system frequency. The addressing circuitry provides multiple pixels/clock in any user defined scan order to implement a wide range of neighborhood operations. With the saving of 83% BRAM resources, the buffer architecture operates at 278 MHz on Xilinx Artix-7 FPGA with an efficiency of 1.3 clock/pixel. It is thus capable to fulfill real time image processing requirements for HD image resolution (1080 × 1920) @103 fcps.
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Het tekort aan handjes in de accountancy neemt toe. Tegelijk groeit de maatschappelijk druk om bedrijven zo goed mogelijk te controleren, om te zorgen dat ze financieel, fiscaal en qua duurzaamheid in de pas blijven lopen met de (toenemende) regelgeving. Gelukkig komt er steeds meer technologie voorhanden die de accountant kan helpen bij het controleren van de boeken, schetst Eric Mantelaers, hoofd Bureau Vaktechniek, RSM Accountants. Medio juni is hij aan de Open Universiteit gepromoveerd op zijn proefschrift ‘An evaluation of technologies to improve auditing’.
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