No abstract

No abstract

No abstract

The Middle to Upper Cenomanian Halal and Turonian Wata formations crop out at Gabal Minsherah, Gabal Yelleg and Gabal Maaza in the northern Sinai Peninsula, Egypt. This paper describes the rudist assemblages of the two formations in a sequence stratigraphic framework. Tabular thickets of conical to cylindrical elevator radiolitid rudists were the most common benthic type on the northern Cenomanian – Turonian Sinai shelf. The thickets were either single beds or multiple beds intercalated with marl or packstone. Most biostromes were laterally restricted and do not extend to nearby outcrops. The Cenomanian rudist biostromes are thin and composed mainly of several species of Radiolitidae and less common Caprinidae together with coralline sponges and benthic foraminifers. The Turonian rudist biostromes are composed of several species of Radiolitidae. The Cenomanian Halal Formation grades upward from basal quartz arenite into bioclastic-oolitic grainstone overlain by bioclastic packstone and wackestone. Dolomite beds are part of the highstand facies. The Formation is composed of transgressive-regressive Halal Sequences 1 and 2. The base of the overlying Wata Formation is Sequence Boundary 3 at the base of Wata Sequence 3, which is Lower to Middle Turonian. The sequence boundary between the Halal and the Wata is marl-on-marl with Upper Cenomanian ammonites overlain by a condensed interval with ammonites of several Lower Turonian zones that are particularly well exposed at Gabal Minsherah. The boundary is interpreted by graphic correlation as a million-year-long hiatus after which carbonate deposition resumed and low-diversity rudist assemblages recovered. The hiatus is correlated to the global anoxic event OAE 2. Following OAE 2 carbonate deposition resumed and produced microfacies similar to those of the Cenomanian. The Upper Turonian Wata Formation is composed of Wata Sequences 4 and 5.

No abstract

This paper presents a path-planning optimization study for a Computer Numerical Control (CNC) machining center tasked with machining jobs involving a large number of holes to drill that are mostly arranged in concentric circular patterns. Benefits of this research may contribute to shortening the machining time in certain components used in heat exchangers, boilers, condensers, trammel screens and food separators. Optimization of tool travel distance and machining cost are typically overlooked aspects when generating tool paths and CNC codes from commercially available CAD software packages. Tool path travel distance minimization can be modelled Travelling Salesman Problem (TSP). Optimization algorithms have been heavily applied in the literature to the TSP with varying levels of success. Ant Colony Optimization (ACO) is one of the most prominent approaches that mimics the natural behavior of ant colonies. The research in this paper proposes a hybrid ACO that has a biasing mechanic designed to take advantage of the geometric hole-pattern arrangement, as well as a local search. Simulation examples show the proposed approach exhibiting superior performance compared to the classic ACO approach, a genetic algorithm (GA) approach, as well as the simple spiral path generated via commercial CAD software. The proposed approach is then applied to the drilling path planning of a two-thousand-hole food-industry separator plate.

Aptian to early Albian times are marked by various geodynamic and paleoenvironmental events such as large igneous province volcanism , perturbations of climate and the carbon cycle, and sea-level changes. The Essaouira-Agadir basin (EAB), located on the Atlantic passive margin of Morocco, offers good and fossiliferous exposures of the Aptian-Albian sedimentary series. A detailed analysis of this succession made it possible to establish a biostratigraphic framework. The identification of discontinuities allowed to define eight depositional sequences. As most of them are correlatable with depositional sequences of other Tethyan areas, they suggest that eustacy was the main parameter controlling sedimentation. The analysis of sedimentary facies and nannofossil assemblages provides information on paleoenvironmental changes. Sedimentation in the EAB evolved from a very low energy, carbonate ramp in the early Aptian to a low energy, slightly deeper, mixed carbonate-clastic ramp in the early Albian. This change occurred along with an increase of clastic input, a change from oligotrophic to mesotrophic faunal assemblages, and a decrease of sea-surface temperatures. The occurrence of current sedimentary features, sporadic dysaerobic deposits and local phosphatic and glauconitic crusts suggests that upwelling currents were significant during this period. Paleogeographic and isopach maps support a transgressive trend in the late Aptian and early Albian, and unravel subsidence anomalies suggesting mild halokinetic movements during Aptian-early Albian times.

No abstract