Automated weighing by sequential inference in dynamic environments

We demonstrate sequential mass inference of a suspended bag of milk powder from simulated measurements of the vertical force component at the pivot while the bag is being filled. We compare the predictions of various sequential inference methods both with and without a physics model to capture the system dynamics. We find that non-augmented and augmented-state unscented Kalman filters (UKFs) in conjunction with a physics model of a pendulum of varying mass and length provide rapid and accurate predictions of the milk powder mass as a function of time. The UKFs outperform the other method tested - a particle filter. Moreover, inference methods which incorporate a physics model outperform equivalent algorithms which do not.Comment: 5 pages, 7 figures. Copyright IEEE (2015

Navigation by Induction-Based Magnetoreception in Elasmobranch Fishes

A quantitative frequency-domain model of induction-based magnetoreception is presented for elasmobranch fishes. We show that orientation with respect to the geomagnetic field can be determined by synchronous detection of electrosensory signals at harmonics of the vestibular frequency. The sensitivity required for this compass-sense mechanism is shown to be less than that known from behavioral experiments. Recent attached-magnet experiments have called into doubt the induction-based mechanism for magnetoreception. We show that the use of attached magnets would interfere with an induction-based mechanism unless relative movement between the electrosensory system and the attached magnet is less than 100 μm. This suggests that further experiments may be required to eliminate induction as a basis for magnetoreception

A Comparison of Genetic Programming with Genetic Algorithms for Wire Antenna Design

This work compares the performance of genetic programming (GP) against traditional fixed-length genome GA approaches on the optimization of wire antenna designs. We describe the implementation of a GP electromagnetic optimization system for wire structures. The results are compared with the traditional GA approach. Although the dimensionality of the search space is much higher for GP than GA, we find that the GP approach gives better results than GA for the same computational effort. In addition, we find that a more expressive antenna structure grammar, dramatically, improves the performance of the GP approach

Traveling Granular Segregation Patterns in a Long Drum Mixer

Mixtures of granular media often exhibit size segregation along the axis of a partially-filled, horizontal, rotating cylinder. Previous experiments have observed axial bands of segregation that grow from concentration fluctuations and merge in a manner analogous to spinodal decomposition. We have observed that a new dynamical state precedes this effect in certain mixtures: bi-directional traveling waves. By preparing initial conditions, we found that the wave speed decreased with wavelength. Such waves appear to be inconsistent with simple PDE models which are first order in time.Comment: 11 page

From low-conflict polity to democratic civil peace: Explaining Zambian exceptionalism

An absence of civil war and other significant sub-state violence makes Zambia an exceptional although not unique case in central-southern Africa. The literature devoted to explaining civil war has grown dramatically in recent years, but while it pays much attention to sub-Saharan Africa only rarely does it investigate counterfactual cases like Zambia. Similarly the growing field of research into post-conflict reconstruction fails to capture the distinct features of persistently low-conflict situations where many of the predisposing conditions for violent conflict might seem to be present. This paper examines Zambia’s experience against a background of general theories that try to explain conflict. It is an “interpretative case study”. The paper proceeds by substantiating Zambia’s claim to a relatively peaceful record and introduces ideas of conflict and conflict theories, before arguing that no single general theory dwelling on just one primary “cause” will suffice to explain Zambian exceptionalism. The precise mix of arguments differs for each one Zambia’s three republican eras, as the potential threats to peace have themselves evolved over the period since independence. The paper’s main theoretical claim is that over time the explanation is both multi-layered and dynamic. That said, certain features do stand out, most notably an inherited political culture that is predisposed against the violent resolution of conflict and continues to insulate the country against social and economic traumas and democratic shortcomings

A new system of refraction for use by the general practitioner

CITATION: Molteno, A. C. B. & Molteno, T. E. S. 1977. A new system of refraction for use by the general practitioner. South African Medical Journal, 52(9):354-355.The original publication is available at https://journals.co.zaA rapid, simple and economical method of refraction with a circular slide rule is descriptionbed.https://journals.co.za/content/m_samj/52/9/AJA20785135_18109Publisher’s versio