The Production Guide for the Zarqaliyya (Universal Astrolabe) in the Work of Abu al-Hasan al-Marrakushi

One of the greatest astronomers of the 13th century, Abū ʿAlī al-Ḥasan al-Marrākushī is the author of Jāmiʿ al-mabādī’ wa-l-ghāyāt fī ʿilm al-mīqāt (An A to Z of Astronomical Timekeeping) which includes the production and operation guides for many astronomical instruments. This study translates the production guide Zarqāliyya, examines the working principle of this instrument, and presents a mathematical interpretation for current readers. A standard astrolabe provides measurements by means of disks produced separately for the different latitudes. The particular disk we examine in this article was developed by the Andalusian astronomer al-Zarqālī (d. 493/1100), is named zarqāliyya, and is known as ṣafīḥa in the West. This disk is peculiar to Islamic astronomy and enables measurement for any latitude. At present, this astrolabe is qualified as universal for being operational independent of latitude. Marrākushī’s discussion of this universal disk zarqāliyya in his time is an epitome for the understanding of the transmission and circulation of knowledge in the scientific environment of Islam, and the current article evaluates this aspect. This article includes the subject and importance of Marrākushī’s monumental work, its modern presentations, and the mathematical explanations of the universal astrolabe’s stereographic projection. It additionally provides the formulations necessary for constructing this astrolabe and presents drawings based on these relations using the Paris edition of the manuscript registered as Or. No.2507-2508 in the National Library of France. The stars and coptic months engraved on the instruments are presented as tables. Lastly, this study includes an annotated translation by comparing the different editions of the manuscript

Amber in prehistoric Iberia: New data and a review.

Provenancing exotic raw materials and reconstructing the nature and routes of exchange is a major concern of prehistoric archaeology. Amber has long been recognised as a key commodity of prehistoric exchange networks in Europe. However, most science-based studies so far have been localised and based on few samples, hence making it difficult to observe broad geographic and chronological trends. This paper concentrates on the nature, distribution and circulation of amber in prehistoric Iberia. We present new standardised FTIR analyses of 22 archaeological and geological samples from a large number of contexts across Iberia, as well as a wide scale review of all the legacy data available. On the basis of a considerable body of data, we can confirm the use of local amber resources in the Northern area of the Iberian Peninsula from the Palaeolithic to the Bronze Age; we push back the arrival of Sicilian amber to at least the 4th Millennium BC, and we trace the appearance of Baltic amber since the last quarter of the 2nd Millennium BC, progressively replacing Sicilian simetite. Integrating these data with other bodies of archaeological information, we suggest that the arrival of Baltic amber was part of broader Mediterranean exchange networks, and not necessarily the result of direct trade with the North. From a methodological perspective, thanks to the analyses carried out on both the vitreous core and the weathered surfaces of objects made of Sicilian simetite, we define the characteristic FTIR bands that allow the identification of Sicilian amber even in highly deteriorated archaeological samples

Polynomial-Time Verification and Testing of Implementations of the Snapshot Data Structure

We analyze correctness of implementations of the snapshot data structure in terms of linearizability. We show that such implementations can be verified in polynomial time. Additionally, we identify a set of representative executions for testing and show that the correctness of each of these executions can be validated in linear time. These results present a significant speedup considering that verifying linearizability of implementations of concurrent data structures, in general, is EXPSPACE-complete in the number of program-states, and testing linearizability is NP-complete in the length of the tested execution. The crux of our approach is identifying a class of executions, which we call simple, such that a snapshot implementation is linearizable if and only if all of its simple executions are linearizable. We then divide all possible non-linearizable simple executions into three categories and construct a small automaton that recognizes each category. We describe two implementations (one for verification and one for testing) of an automata-based approach that we develop based on this result and an evaluation that demonstrates significant improvements over existing tools. For verification, we show that restricting a state-of-the-art tool to analyzing only simple executions saves resources and allows the analysis of more complex cases. Specifically, restricting attention to simple executions finds bugs in 27 instances, whereas, without this restriction, we were only able to find 14 of the 30 bugs in the instances we examined. We also show that our technique accelerates testing performance significantly. Specifically, our implementation solves the complete set of 900 problems we generated, whereas the state-of-the-art linearizability testing tool solves only 554 problems

The BG News February 11, 1999

The BGSU campus student newspaper February 11, 1999. Volume 82 - Issue 97https://scholarworks.bgsu.edu/bg-news/7445/thumbnail.jp

On the underestimated effect of the starch ash on the characteristics of low cost ceramic membranes

Starches are commonly used as a pore generator in the fabrication of low-cost ceramic membranes, since they are cheap, innocuous, environmentally friendly and easy to burn. Nevertheless, the influence of starches residues (ashes) generated during its burning off is dismissed. The present study analyses the influence of the starch ashes, generated by six different starches of similar particle size, on the characteristics of low-cost ceramic supports. The results indicated that starches gave rise to different amounts of ashes ranging from 0.17 to 0.71 wt%. In addition, these ashes contained some chemical elements in their composition, such as sodium, potassium or calcium, which can act as fluxes in the ceramic composition, modifying the characteristics of the obtained supports (mainly open porosity, water permeability and pore size distribution). It has also been observed that when the ash content grows the effect of the fluxing elements on the evolution of the microstructural features of the ceramic membrane (porosity, pore size or permeability) becomes more significant. Finally, tortuosity was calculated with a simple model derived from the Hagen–Poiseuille equation; the obtained data showed that tortuosity factor and its evolution with dwelling time were also affected by the starch ashes.This material is based upon work supported by the Spanish Ministry of Science and Innovation through the National Plan for Scientific Research, Development and Technology Innovation 2008–2011 (INNPACTO programme, project IPT-2011–1069-310000)

The BG News January 20, 2000

The BGSU campus student newspaper January 20, 2000. Volume 85 - Issue 7https://scholarworks.bgsu.edu/bg-news/7588/thumbnail.jp

Parallel bug-finding in concurrent programs via reduced interleaving instances

Concurrency poses a major challenge for program verification, but it can also offer an opportunity to scale when subproblems can be analysed in parallel. We exploit this opportunity here and use a parametrizable code-to-code translation to generate a set of simpler program instances, each capturing a reduced set of the original program’s interleavings. These instances can then be checked independently in parallel. Our approach does not depend on the tool that is chosen for the final analysis, is compatible with weak memory models, and amplifies the effectiveness of existing tools, making them find bugs faster and with fewer resources. We use Lazy-CSeq as an off-the-shelf final verifier to demonstrate that our approach is able, already with a small number of cores, to find bugs in the hardest known concurrency benchmarks in a matter of minutes, whereas other dynamic and static tools fail to do so in hours

Two swords from the foundation of Gibraltar

The two swords plus their associated acabbard and belt or baldric fragments which were found in Matin’s Cave, Gibraltar, date from the 12th century AD. Such dating is supporting the design to the objects themselves, their cultural-historical context, and their varied decoration. This evidence is also used to propose that the ensemble was all of Andalusian of North African origin, and as such represents an almost unique survival of 12th century western Islamic military equipment.Las dos espadas, junto con sus correspondientes vainas y restos de cinto o tahalí, halladas en Martin’s Cave (Gibraltar), deben fecharse en el siglo XII d.C. Esta datación se basa en la tipología de los objetos, en su contexto histórico-cultural, y en su variada decoración. Estos datos se emplean también para proponer que el conjunto es de origen Andalusí o Norteafricano, y que por tanto representan un caso casi único de preservación de equipo militar islámico occidental del s. XII