The Plant Propagation Algorithm on Timetables: First Results

One Stochastic HillClimber and two implementations of the Plant Propagation Algorithm (PPA-1 and PPA-2) are applied to an instance of the University Course Timetabling Problem from the Univer- sity of Amsterdam. After completing 10 runs of 200,000 objective function evaluations each, results show that PPA-1 outperforms the HillClimber, but PPA-2 makes the best timetables

Identification of Pre-1950 Synthetic Organic Pigments in Artists’ Paints. A Non-Invasive Approach Using Handheld Raman Spectroscopy

There is little information on the actual use of early synthetic organic pigments (SOPs) in art objects, especially those from before 1950. Their presence can, however, pose a challenge to conservation because their chemical composition, as well as their lightfastness and sensitivity to solvents, are often unknown. Here, a study on the non-invasive identification of SOPs in historic pre-1950 varnished paint-outs from artists’ materials manufacturer Royal Talens is presented. The paints were analysed using a handheld Raman device. Spectra were evaluated by recording the spectra of the same samples with a benchtop instrument. This study demonstrated that the identification of SOPs in varnished oil paints with a non-invasive approach is possible and rather straightforward. The handheld Raman device allowed us to identify fourteen SOPs from eight pigment classes. Besides the occurrence of expected and the known SOPs of this time period, there were also some surprising results, like the detection of the triarylcarbonium pigments PG2 and PB8, and the monoazo Mordant Yellow 1

Bias-based modeling and entropy analysis of PUFs

Physical Unclonable Functions (PUFs) are increasingly becoming a well-known security primitive for secure key storage and anti-counterfeiting. For both applications it is imperative that PUFs provide enough entropy. The aim of this paper is to propose a new model for binary-output PUFs such as SRAM, DFF, Latch and Buskeeper PUFs, and a method to accurately estimate their entropy. In our model the measurable property of a PUF is its set of cell biases. We determine an upper bound on the ‘extractable entropy’, i.e. the number of key bits that can be robustly extracted, by calculating the mutual information between the bias measurements done at enrollment and reconstruction. In previously known methods only uniqueness was studied using information-theoretic measures, while robustness was typically expressed in terms of error probabilities or distances. It is not always straightforward to use a combination of these two metrics in order to make an informed decision about the performance of different PUF types. Our new approach has the advantage that it simultaneously captures both of properties that are vital for key storage: uniqueness and robustness. Therefore it will be possible to fairly compare performance of PUF implementations using our new method. Statistical validation of the new methodology shows that it clearly captures both of these properties of PUFs. In other words: if one of these aspects (either uniqueness or robustness) is less than optimal, the extractable entropy decreases. Analysis on a large database of PUF measurement data shows very high entropy for SRAM PUFs, but rather poor results for all other memory-based PUFs in this database

English medium of instruction: A situation analysis

The majority of learners in southern Africa receive their education through the medium of a second language, English. Although teachers of English play a crucial role in helping learners to acquire language skills in the medium of instruction, we argue that subject content teachers' lack of attention to the teaching of the four language skills may be a raison d'être for learners' lack of academic achievement. A situation analysis conducted among three study populations examined the extent to which subject content teachers took responsibility for the teaching of language skills in the content classroom, as well as possible reasons for not doing so. It also shed some light on the amount of language teaching that actually took place in a content classroom. The aim of the situation analysis was to determine whether there was a need for a specialised training course for English second language medium of instruction teachers.South African Journal of Education Vol. 27 (1) 2007: pp. 69-8

An integrated course for English medium of instruction teacher trainees in South Africa

Research regarding the specific needs of the L2MI teacher points to the need for developing a training course that not only ensures advanced levels of personal proficiency in the medium of instruction, but also certifies the ability to apply methodological and presentational skills that enhance and promote learning in the L2MI subject content classroom. This article describes the design and implementation of an integrated course for second language medium of instruction (L2MI) teacher trainees. Based upon the profile of effective L2MI and deriving outcomes for language,methodological and presentational skills from this, the course is both practical and functional. The hybrid model that was used for the design of the course is based on a combination of an Outcomes-based and a Backward Design model for course design and consists of six distinctive steps. The integrated course was developed within the BEd teacher-training programme and introduced for one semester. The students and the course instructor reviewed some aspects of the course and the Instructional Planafterwards.Keywords: English medium of instruction; second language medium of instruction; outcomes-based education; backward design; course design; teacher training

Performance of TCP with multiple Priority Classes

We consider the dimensioning problem for Internet access links carrying TCP traffic with two priority classes. To this end, we study the behaviour of TCP at the flow level described by a multiple-server Processor Sharing (PS) queueing model with two customer classes, where the customers represent flows generated by downloading Internet objects; the sojourn times represent the object transfer times. We present closed-form expressions for the mean sojourn times for high-priority customers and approximate expressions for the mean sojourn times of low-priority customers. The accuracy of the model is demonstrated by comparing results based on the PS model with "real" TCP simulation results obtained by the well-known Network Simulator. The experimental results demonstrate that the model-based results are highly accurate when the mean object size is at least 10 IP-packets, and the loss rate is negligible

Some studies on the deformation of the membrane in an RF MEMS switch

Radio Frequency (RF) switches of Micro Electro Mechanical Systems (MEMS) are appealing to the mobile industry because of their energy efficiency and ability to accommodate more frequency bands. However, the electromechanical coupling of the electrical circuit to the mechanical components in RF MEMS switches is not fully understood. In this paper, we consider the problem of mechanical deformation of electrodes in RF MEMS switch due to the electrostatic forces caused by the difference in voltage between the electrodes. It is known from previous studies of this problem, that the solution exhibits multiple deformation states for a given electrostatic force. Subsequently, the capacity of the switch that depends on the deformation of electrodes displays a hysteresis behaviour against the voltage in the switch. We investigate the present problem along two lines of attack. First, we solve for the deformation states of electrodes using numerical methods such as finite difference and shooting methods. Subsequently, a relationship between capacity and voltage of the RF MEMS switch is constructed. The solutions obtained are exemplified using the continuation and bifurcation package AUTO. Second, we focus on the analytical methods for a simplified version of the problem and on the stability analysis for the solutions of deformation states. The stability analysis shows that there exists a continuous path of equilibrium deformation states between the open and closed state