Laboratory Notes,Laboratory Experiences,and Conceptual Analysis: Understanding the Making of Ohm's First Law in Electricity

Georg Simon Ohm's work in the field of electricity led to what is now considered to be the most fundamental law of electrical circuits, Ohm's Law. Much less known is that only months earlier, Ohm had published another law—one that differed significantly from the now accepted one. The latter entailed a logarithmic relation between the length of the conductor and a parameter that Ohm called “loss of force.” This paper discusses how Ohm came up with an initial law that he felt compelled to correct a few months later. We analyze Ohm's publication as well as his laboratory notes, relating them to our own laboratory experiences while using the replication method to study his work. We also discuss the conceptual background of Ohm's work. We conclude that he was significantly influenced by French studies in the field of electricity, most notably the ones by Charles Augustin Coulomb.     

TIME SERIES AND TURNING POINT FORECASTS: A COMPARISON OF ASSOCIATIVE MEMORIES AND BAYESIAN ECONOMETRIC TECHNIQUES APPLIED TO LESAGE'S DATA*

ABSTRACT. Associative memory techniques are drawn from the artificial intelligence literature, and have demonstrated considerable utility for parameter identification in dynamical systems. Previous turning point forecasts constructed by LeSage are compared to forecasts generated by associative memories and simple autoregressive models. Both the associative memories and the autoregressions perform as well or better than the more complicated econometric procedures described by LeSage, with the exception of West and Harrison's (1989) dynamic linear model specification. Extensions are suggested.     

Forecasting in a Small and Unstable Regional Economy Using Regime Shifting Models: The Case of Extremadura

We consider forecasting in a small and unstable regional economy subject to structural breaks. In this context, we work with two types of regime‐shifting databased models using cointegration theory. The objective of the present work is to analyze the out‐of‐sample forecasting performance of the two approaches used to construct a short‐term regional econometric model: stochastic and deterministic time varying parameters models. The forecasting experiments will be illustrated by specifying, and estimating an econometric model for Extremadura, a small and unstable region in southwestern Spain.     

The Mediterranean Lateen Sail in Late Antiquity

The Mediterranean lateen sailing rig has been studied since the early-to-mid-20th century. Recently-published depictions of sailing vessels rigged with lateen and settee sails, dating to the late-antique period, allow some of the principle characteristics of that rig to be established. This allows comparison with lateen- or settee-rigged vessels from both earlier and later periods. The sailing rigs depicted on other vessels can be identified and the level of technical continuity between the late-antique and medieval Mediterranean addressed. Finally it is possible to assess the extent to which the lateen sail was established in the Mediterranean by late antiquity.
© 2009 The Author     

A technological transition in Mongolia evident in microstructure,chemical composition and radiocarbon age of cast iron artifacts

Metallurgical examination of cast iron objects from the Khitan period (AD 10th–12th) in Mongolia shows that they might be classified into two groups. The first is based on Fe–C alloys of near eutectic composition and the second is based on Fe–C–Si alloys with reduced carbon content and numerous sulfide inclusions. By contrast, all the objects from the succeeding Mongolian empire period (AD 12th–15th) belong to the second group, indicating that a technological transition had occurred during the Khitan period. Accelerator mass spectrometry (AMS) on carbon samples extracted from artifacts in both groups and measurement of alloy compositions suggest that the use of mineral coal in smelting was a major factor for this transition.     

Quantifying Ship Shape in Archaeology: Evaluating 3D Geometric Morphometrics

The analysis of the archaeological remains of ships and boats, in particular hull shapes, have been central to wider analysis of performance, function, and significance within past societies. This article reviews established methods of quantifying shape in ship and boat archaeology—linear measurement ratios and form coefficients—and evaluates the utility of 3D geometric morphometrics (GM). The 3D shape of 30 vessels from north‐west Europe dating between 325 BC and AD 1915 are quantified to study how hull shape relates to a vessel's function and intended operating environment. A comparison of the three methods highlights the importance of analysing the complexity of a hull in a holistic manner and demonstrates that 3D GM outperforms the traditional methods.