Register Transducers Are Marble Transducers

Deterministic two-way transducers define the class of regular functions from words to words. Alur and Cerný introduced an equivalent model of transducers with registers called copyless streaming string transducers. In this paper, we drop the “copyless” restriction on these machines and show that they are equivalent to two-way transducers enhanced with the ability to drop marks, named “marbles”, on the input. We relate the maximal number of marbles used with the amount of register copies performed by the streaming string transducer. Finally, we show that the class membership problems associated with these models are decidable. Our results can be interpreted in terms of program optimization for simple recursive and iterative programs.SCOPUS: cp.pinfo:eu-repo/semantics/publishe

Integrated studies for the evaluation of conservation treatments on buildings materials from archaeological sites: application to the case of Merida (Spain)

The application of conservation treatments, such as consolidation and protection ones, has been demonstrated ineffective in many cases, and even harmful. Evaluation studies should be a mandatory task, ideally before and after the intervention, but both tasks are complex and unusual in the case of archaeological heritage. This study is mainly focused on analyzing changes in petrophysical properties of stone material from archaeological sites of Merida (Spain), evaluating, both on site and in laboratory, effects derived from different conservation treatments applied in past interventions, throughout the integration of different non-destructive techniques (NDT) and portable devices of analysis available at the Institute of Geosciences (CSIC,UCM). These techniques allow, not only assessment of effectiveness and alteration processes, but also monitoring durability of treatments, focused mainly on 1996 intervention in the case of Roman Theater, as well as different punctual interventions from the 90?s until date in the House of Mitreo. Studies carried out on archaeological sites of Merida permit us to compare outcomes and also check limitations in the use of those equipments. In this paper we discuss about the use of some techniques, their integration and limits, for the assessment of conservation treatments, showing some examples of Merida?s case study

Nonlinear Ball Chain Waveguides For Acoustic Emission And Ultrasound Sensing Of Ablation

Harsh environment acoustic emission and ultrasonic wave sensing applications often benefit from placing the sensor in a remote and more benign physical location by using waveguides to transmit elastic waves between the structural location under test and the transducer. Waveguides are normally designed to have high fidelity over broad frequency ranges to minimize distortion - often difficult to achieve in practice. This thesis reports on an examination of using nonlinear ball chain waveguides for the transmission of acoustic emission and ultrasonic waves for the monitoring of thermal protection systems undergoing severe heat loading, leading to ablation and similar processes. Experiments test the nonlinear propagation of solitary, harmonic and mixed harmonic elastic waves through a copper tube filled with steel and elastomer balls and various other waveguides. Triangulation of pencil lead breaks occurs on a steel plate. Data are collected concerning the usage of linear waveguides and a water-cooled linear waveguide. Data are collected from a second water-cooled waveguide monitoring Atmospheric Reentry Materials in UVM\u27s Inductively-Coupled Plasma Torch Facility. The motion of the particles in the dimer waveguides is linearly modeled with a three ball and spring chain model and the results are compared per particle. A theoretical nonlinear model is presented which is capable of exactly modeling the motion of the dimer chains. The shape of the waveform propagating through the dimer chain is modeled in a sonic vacuum. Mechanical pulses of varying time widths and amplitudes are launched into one end of the ball chain waveguide and observed at the other end in both time and frequency domains. Similarly, harmonic and mixed harmonic mechanical loads are applied to one end of the waveguide. Balls of different materials are analyzed and discriminated into categories. A copper tube packed with six steel particles, nine steel or marble particles and a longer copper tube packed with 17 steel particles are studied with a frequency sweep. The deformation experienced by a single steel particle in the dimer chain is approximated. Steel ball waveguides and steel rods are fitted with piezoelectric sensors to monitor the force at different points inside the waveguide during testing. The corresponding frequency responses, including intermodulation products, are compared based on amplitude and preloads. A nonlinear mechanical model describes the motion of the dimer chains in a vacuum. Based on the results of these studies it is anticipated that a nonlinear waveguide will be designed, built, and tested as a possible replacement for the high-fidelity waveguides presently being used in an Inductively Coupled Plasma Torch facility for high heat flux thermal protection system testing. The design is intended to accentuate acoustic emission signals of interest, while suppressing other forms of elastic wave noise

Unsteady Aerodynamics and Blade-Row Interactions in the Embedded Stage of an Axial Compressor

In a mature engineering field like compressor aerodynamics, the most accessible advances in machine technology, translating to performance and efficiency, have been discovered and have found industry design applications. As the community continues to make progress, increasingly challenging aspects of the involved physics must be exploited. Modern turbomachinery operates with larger bypass ratios, smaller cores, and lighter, thinner, and more flexible materials resulting in the maintenance of higher operating pressures and temperatures. As the performance and efficiency of these machines continues to climb, the same technological advances reinforce challenges like forced-response vibration, high-cycle fatigue of engine components, and large relative tip clearances in an engine core. Accounting for these challenges increasingly depends on the investigation of the unsteady domain for solutions. Tools at the disposal of the designer include progressively improving computational simulations through both computational resources and attainable model fidelity. As essential as these tools are for modern turbomachinery design, the confidence in their results is only as good as the experimental data used to validate them. The objective of this research is the experimental investigation and characterization of the transient aerodynamics and blade-row interactions near forced-response resonant vibratory operating conditions in a multi-stage environment. Experimental methods are focused on fast-response pressure transducers with the high frequency response capable of capturing the unsteady pressure fluctuations associated with the high-speed rotation and blade-pass frequency of a modern high-pressure core axial compressor. Investigation is centered on an engine-representative embedded rear stage, with adjacent stages establishing realistic flow conditions and resulting boundary conditions for model comparison. Aerodynamic characterization of several flow conditions and the examination of the effect of a reduced vane-count stator configuration upstream of the embedded stage are performed with measurements of the embedded rotor at the casing endwall and rotor exit plane, as well as within a passage of the embedded stator. Circumferential vane traverse around stationary instrumentation provide a full vane passage of phase-locked, time-resolved pressure measurements of the rotor aerodynamics and the unsteady loading of the embedded stator is distinguished for a single vane position. Results from this investigation identify and describe the inception and trajectory of tip clearance flows, including the tip leakage vortex and double-leakage tip clearance flow. Evidence of an upstream vane wake interaction with the rotor occurs for limited regions of vane passage positions. Spectral analyses and pressure unsteadiness provide further insight into the blade-row interactions

Non-Destructive Techniques Applied to Monumental Stone Conservation

Non-destructive techniques have always been used in the study of built cultural heritage because of the high cultural value of the concerned objects and the need to preserve them as intact as possible. In this chapter, different non-destructive techniques applied to the conservation of historical building are presented. The selected techniques concern the measurement of some physical properties of the building materials measured at the surface: water absorption, permeability, water content, cohesion, hardness and so on; the actual conditions of the building: stress state, deformation, crack growth and so on; and in-depth physical properties: mechanical properties, inner structure of walls, damp location and salt content. Some of these techniques are used for inspection of the building at a given time, whereas others can be applied for long periods of time to investigate the evolution of the building or of one of its parts (e.g., crack propagation) with time