3,101 research outputs found

    A RECONSTRUCTION OF THE GREEK-ROMAN REPEATING CATAPULT

    Get PDF
    An “automatic” repeating weapon used by the Roman army is presented. Firstly a short description is shown of the working principle of the torsion motor that powered the Greek-Roman catapults. This is followed by the description of the reconstructions of these ancient weapons made by those scientists who studied repeating catapults. The authors then propose their own reconstruction. The latter differs from the previous ones because it proposes a different working cycle that is almost automatic and much safer for the operators. The authors based their reconstruction of the weapon starting from the work of previous scientists and on their own translation of the original text (in ancient Greek) by Philon of Byzantium

    Markedly different ATP requirements for rRNA synthesis and mtDNA light strand transcription versus mRNA synthesis in isolated human mitochondria

    Get PDF
    In isolated mitochondria from HeLa cells, the ATP requirements for mitochondral DNA (mtDNA) transcription and RNA processing can be satisfied by either endogenous synthesis, mainly through oxidative- phosphorylation, or by exogenous supply. The pattern of RNA synthesis changes dramatically depending upon the level of ATP available. At the low intramitochondrial ATP levels produced from endogenous ADP in the presence of an oxidizable substrate and phosphate, the mRNA species are labeled to a substantial extent, whereas there is only a marginal labeling of the rRNA species and light (L) strand transcripts. By contrast, high ATP levels, either provided exogenously or produced endogenously in the presence of an oxidizable substrate, phosphate, and exogenous ADP, strongly stimulate rRNA synthesis (about 10-fold) and light (L) strand transcription (greater than 10-fold), with only a slight increase in mRNA synthesis

    A Liner Shipping Speed Optimization Model to Reduce Bunker Cost and Pollutants Emitted

    Get PDF
    Environmental impact has become one of the most relevant issues in liner shipping during the recent years. Maritime shipping is responsible for the 2.7 per cent of the world CO2 emissions, of which 25 per cent is attributable to container ships. This business also produces a significant quantity of sulphur, a very dangerous substance for human health, especially if it is emitted in areas next to the coast. At the same time, bunker cost represents the biggest portion of the operational cost of a shipping company. Slow steaming is a cheap and effective strategy from both save pollutants emissions and bunker cost. Moreover, it can be immediately put into practice. This report introduces a Mixed Integer Programming Model to solve the Liner Shipping Routing and Speed Optimization Problem (LSRSOP). The final goal is to find the best route and to optimize the the sailing speed of the vessel considering the Emission Control Areas and maximum transit times between ports. Two Heuristic Methods -the 2-Steps Method and the Simulated Annealingare proposed to solve big instances that would require too much running time to be solved until optimality. Both of them use a Hill-Climbing Algorithm that generates a slight different route from a given one. A Bi-Objective Function Model has been designed for instances whose the optimal solution can be found in reasonable time. It considers the operative cost of the vessel and the external cost of emissions. The results show efficient solutions that are the "golden line" between the most convenient solution for the company and the most sustainable solution

    An Underactuated Multi-finger Grasping Device

    Get PDF
    In this paper, a mechanical model for an underactuated multi-finger grasping device is presented. The device has single-tendon, three-phalanx fingers, all moved by only one actuator. By means of the model, both the kinematic and dynamical behaviour of the finger itself can be studied. The finger is part of a more complex mechanical system that consists of a four-finger grasping device for robots or a five-finger human hand prosthesis. Some results of both the kinematic and dynamical behaviour are also presented

    A New Real Time Shape Acquisition with a Laser Scanner: First Test Results

    No full text
    Abstract The first results of a new method for real-time shape acquisition with a laser scanner are presented. The new method is essentially based on the use of a laser beam and a web-cam. A digital filter parameters identification was studied for the laser line detection in the image. After this, a model for the reconstruction in real-time of the laser line in the space was developed. The firsttest rig was just conceived to validate the method; hence, no high resolution cameras were adopted. Nevertheless, the tests have showed encouraging results. Tests were made on both plane and non-plane surfaces. First of all, it was confirmed that it is possible to calibrate the intrinsic parameters of the video system, the position of the image plane and the laser plane in a given frame, all in the same time. Moreover the surface shapes were recognized and recorded with an appreciable accuracy. The tests also showed that the proposed method can be used for robotic applications, such as robotic kinematic calibration and 3D surfaces recognition and recording. For this last purpose, the test rig is fitted on a robot arm that permits to the scanner device to ‘observe’ the 3D object from different and known positions

    Robot Assisted 3D Shape Acquisition Optical Systems

    Get PDF
    In this chapter, a short description of the basic concepts about optical methods for the acquisition of three-dimensional shapes is first presented. Then two applications of the surface reconstruction are presented: the passive technique Shape from Silhouettes and the active technique Laser Triangolation. With both these techniques the sensors (telecameras and laser beam) were moved and oriented by means of a robot arm. In fact, for complex objects, it is important that the measuring device can move along arbitrary paths and make its measurements from suitable directions. This chapter shows how a standard industrial robot with a laser profile scanner can be used to achieve the desired d-o-f. Finally some experimental results of shape acquisition by means of the Laser Triangolation technique are reported

    Robot assisted 3D shape acquisition by optical systems

    Get PDF
    In this chapter, a short description of the basic concepts about optical methods for the acquisition of three-dimensional shapes is first presented. Then two applications of the surface reconstruction are presented: the passive technique Shape from Silhouettes and the active technique Laser Triangolation. With both these techniques the sensors (telecameras and laser beam) were moved and oriented by means of a robot arm. In fact, for complex objects, it is important that the measuring device can move along arbitrary paths and make its measurements from suitable directions. This chapter shows how a standard industrial robot with a laser profile scanner can be used to achieve the desired d-o-f. Finally some experimental results of shape acquisition by means of the Laser Triangolation technique are reported
    • 

    corecore