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The main objection of this NATO lecture series is the introduction of rigorous study of randomized algorithms for uncertain systems and control, with specific UAV applications. A Randomized Algorithm (RA) is an algorithm that makes random choices during its execution to produce a result. This briefing covers 1) Probabilistic Robustness Analysis and Synthesis; 2) Sequential Methods for Convex Problems; 3) Non-Sequential Methods; 4) A Posteriori Analysis; 5) RACT; and 6) Systems and Control Applications., Presented at the NATO/RTO Systems Concepts and Integration Panel Lecture Series SCI-195 on Advanced Autonomous Formation Control and Trajectory Management Techniques for Multiple Micro UAV Applications held in Glasgow, United Kingdom on 19-21 May 2008. See also ADM002223. The original document contains color images.

Randomized algorithms (RA) are frequently used in many areas of engineering, computer science, physics, finance, optimization, but their appearance in systems and control is mostly limited to Monte Carlo simulations. Main objective of this mini-course is the introduction to rigorous study of RAs for uncertain systems and control, with specific applications. Randomized algorithms are Probably Approximately Correct (PAC). This implies accepting a "small" risk of giving a wrong solution. The risk can be made arbitrarily small (but not zero) taking suitable values of so-called confidence and accuracy., Presented at the NATO/RTO Systems Concepts and Integration Panel Lecture Series SCI-195 on Advanced Autonomous Formation Control and Trajectory Management Techniques for Multiple Micro UAV Applications held in Glasgow, United Kingdom on 19-21 May 2008. See also ADM002223. The original document contains color images.

The Harrison Project is a project dealing with Time and Synchronization Applications started in the framework of the GSA (GNSS Supervisor Authority), a European Union body. The aim of the project is to study the advantages in time and synchronization applications offered by the Galileo System. The project is basically arranged in three major phases: the user community analysis, the development of a solution demonstrator, and the field trials of the demonstrator. The purpose of the project phase is to analyze the time and synchronization applications for each domain and study the advantages offered by the availability of a common precise time reference recovered by the Galileo SIS (Signal in Space). Moreover, this activity is also a stimulus for the development of new ideas. The proposed demonstrator is called the Authenticated and Certified Time Solution (ACTS) and aims to study the feasibility of using the time distributed by the Galileo System authenticated and certified through the Galileo System and added value services. The legal aspects are also considered and a dedicated analysis is performed considering the European Community laws and the acts in the major EU countries. The time distributed through the Galileo Satellite System (and GNSS in general) is very attractive for all those applications that need a high level of synchronization over a wide geographical area; the benefit is that a synchronization network with nodes and a subnetwork is no longer necessary, since all the nodes can directly access the main synchronization SIS., Prepared in cooperation with the European GNSS Supervisory Authority (GSA), Brussells, Belgium. Presented at the Annual Precise Time and Time Interval (PTTI) Meeting (39th), Long Beach, CA on 26-29 Nov 2007 and published in the proceedings of the same, p489-510. The original document contains color images.

The PTF is an Element of the Galileo Mission Segment in charge of generating the Galileo System Time (Master Clock) as the physical time reference of Galileo. The PTF C/D/E1 phase contract acquired by Consorzio Torino Time (Italy) started on December 2005. The detailed design is almost completed and the implementation phase will begin soon. To meet the Galileo system requirements, the time transfer functions have being designed on the basis of three techniques: TWSTFT, CV, and use of OSPF products. The last technique implies interfacing an external facility, i.e. the OSPF (Galileo Orbitography & Synchronization Processing Facility), onboard clocks, and GSS clocks. This paper addresses the current PTF design status, including: * PTF overview * Architecture * Algorithms SW * Time transfer HW * Time transfer performance., Presented at the Annual Precise Time and Time Interval (PTTI) Meeting (39th) held in Long Beach, CA on 26-29 Nov 2007. Published in the Proceedings of the Annual Precise Time and Time Interval (PTTI) Meeting (39th), p439-448, 2007. The original document contains color images.

Long and deep tunnels are characterised by extreme conditions for risk assessment and management throughout a project's life. The report is intended to serve the international tunnelling community as a guideline for their planning, design, construction and operation, with recommendations for methodologies to solve major problems. Specific reference is made to: investigation methods for geological conditions such as high stress, plasticity or squeezing, rock bursts, faults and shear zones with high water pressure, or high ground temperature; management of risks related to great length; construction aspects such as long headings, underground site installations, ventilation, haulage, control of advance rates, support selection and performance; and safety requirements both for general construction and for road and rail operation., Long and deep tunnels are characterised by extreme conditions for risk assessment and management throughout a project's life. The report is intended to serve the international tunnelling community as a guideline for their planning, design, construction and operation, with recommendations for methodologies to solve major problems. Specific reference is made to: investigation methods for geological conditions such as high stress, plasticity or squeezing, rock bursts, faults and shear zones with high water pressure, or high ground temperature; management of risks related to great length; construction aspects such as long headings, underground site installations, ventilation, haulage, control of advance rates, support selection and performance; and safety requirements both for general construction and for road and rail operation.

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The paper describes a method for dealing with multilingual vocabularies in speech recognition tasks. We present an approach that combines acoustic descriptive precision and capability of generalization to multiple languages. The approach is based on the concept of classes of transitions between phones. The classes are defined by means of objective measures on acoustic similarities among sounds of different languages. This procedure stems from the definition of a general language-independent model. When a new language is to be added, the phonological structure of the language is mapped onto the set of classes belonging to the general model. Successively, if a limited amount of language-specific speech data becomes available for the new language, we identify those sounds which require the definition of additional classes. The experiments have been conducted in Italian, English and Spanish languages. The method can also be considered as a way of implementing cross-lingual porting of recognition models for a rapid prototyping of recognizers in a new target language, specifically in cases whereby the collection of large training databases would be economically infeasible., Presented at the Information Systems Technology Panel (IST) Tutorial and Workshop held in Leusden, The Netherlands, 13-14 September 1999. This article is from ADA387529 Multi-Lingual Interoperability in Speech Technology (l'Interoperabilite multilinguistique dans la technologie de la parole)

This paper is concerned with the role played by the ground Structural Coupling Test (SCT) and the update of the aeroservoelastic model in the qualification process of a modern combat aircraft. It represents the completion of Reference 1 after several improvements introduced in the Notch Filter (NF) design procedure, numerous ground test campaigns and the confirmation of flight trials. Most of modern combat aircraft are equipped with fly-by- wire and digital flight control systems (FCS). The problem of interaction between the dynamic response of the airframe and the FCS is usually solved through an appropriate set of notch filters, designed to attenuate the level of structure vibrations picked up by the FCS sensors. Fundamental part of the qualification of the notch filter set is the ground testing up activity, generally known as ground Structural Coupling Test., Presented at the Specialists' Meeting of the RTO Applied Vehicle Technology Panel (AVT) held in Ottawa, Canada, 18-20 Oct 1999. This article is from ADA388195 Structural Aspects of Flexible Aircraft Control (les Aspects structuraux du controle actif et flexible des aeronefs)

The possibility of using a three-level-A-scheme for the excitation of the clock hyperfine transition in Rb87 is analyzed. The physics involved opens up two distinct avenues useful for the implementation of an atomic frequency standard, avenues based on two distinct phenomena: the electro-magnetically induced transparency (EIT or Dark Line) and the coherent microwave emission (Maser without population inversion). In spite of the close connection between the two phenomena, which are generated by the coherence created in the ground state by means of two coherent laser radiation fields (Coherent Population Trapping), the characteristics of an atomic frequency standard based on either of these phenomena may be quite different. The paper discusses the possibility of implementing on the basis of these two phenomena, new Rb87 atomic frequency standards having an excellent frequency stability, and makes explicit their differences., See also ADM001481. Presented at the Precise Time and Time Interval (PTTI) Meeting (31st Annual) held in Dana Point, CA on 7-9 December 1999. Published in the Proceedings of the Precise Time and Time Interval (PTTI) Meeting (31st Annual), p605-614, 1999.

Increasing interest in RCS (Radar Cross Section) reduction is placing new demands on theoretical, computational and graphic techniques for calculating scattering properties of complex targets. In particular, computer codes capable of predicting tile RCS of an entire aircraft at high frequency and of achieving RCS control with modest structural changes, are becoming of paramount importance in stealth design. In this paper, a computer code, evaluating the RCS of arbitrarily shaped metallic objects CAD generated, and its validation with measurements carried out using ALENIA RCS test facilities, are presented, The code, based on the Physical Optics method is characterized by an efficient integration algorithm with error control, ill order to contain the computer time within acceptable limits, and by an accurate parametric representation of the target surface in terms of bicubic splines. RCS, High frequency techniques, Physical Optics, CAD models, RCS reduction., This article is from Target and Clutter Scattering and Their Effects on Military Radar Performance (Diffraction par les Cibles et le Fouillis et ses Effets sur les Performances des Radars Militaires ), AD-A244 893, p16-1 thru 16-13.

The continuous growing in systems/functions installed in the modern aircraft, imposed by the more and more demanding requirements in terms of performance and safety, is leading to the development and the application of new components and systems in the area of cockpit indication and automatic controller integration. The Cathode Ray Tubes (CRT) and other multifunction display technologies are rapidly replacing many of the dials, panels and gauges of the old cockpit. Artificial intelligence and high level automation are emerging in digital avionics. These systems would take over the crew in many cockpit management functions such as reconfiguration to compensate fault or execute emergency procedures. This paper analyzes the design and certification aspects related to the adoption of these new technologies and discusses some aspects of human factor engineering which become an integral part for the cockpit design, for the simbology and for the logic integration of the function within the automatic control and display system., This article is from 'Progress in Military Airlift: The Flight Mechanics Panel Symposium Held in Lisbon, Portugal on 28-31 May 1990 (Les Progres Realises dans le Domaine du Transport Aerien Militaire), AD-A239 471, p9-1 thru 9-8.

The measurements of gravity acceleration described in the report were performed in 1980. The introductory part of the report illustrates the transportable absolute gravimeter and ancillary instrumentation used in measurements, and describes the measurement method applied; uncertainty and errors are analysed as well. Measurements of gravity acceleration made in Europe prior to the USA program are also briefly considered before a detailed account is given of the measurements made in the USA. Numerous tables are provided. Six stations were observed in the USA and approximately 100 measurements made per station. The results show an overall uncertainty in g measurements of the order of 10 microgal.

The measurements of gravity acceleration described in the report were performed in 1977 within a grant program sponsored by the US Air Force. The introductory part of the report illustrates the transportable absolute gravimeter and ancillary instrumentation used in measurements, and describes the measurement method applied; uncertainty and errors are analysed as well. Measurements of gravity acceleration made in Europe prior to the USA program are also briefly considered before a detailed account is given of the measurements made in the USA. The numerous tables in the text and at the end of the report form an essential part of it. Six stations were observed in the USA and approximately 100 measurements made per station. The results show an overall uncertainty in g measurements.

The electromagnetic threat to future aircraft is studied and evaluated on the basis of the evolution of the avionic systems. The high level of integration of these systems combined with the increased number of electromagnetic sources which may interfere with the performances of the overall weapon system create the need of reexamining the usual design and testing approach in order to reach an adequate level of aircraft hardening. It is essential to design and test at system level rather than equipment level: this aim, obviously, is difficult to achieve mainly because of the lack of a well established methodology. The system design guidelines are discussed highlighting areas where basic research studies shall still be undertaken; similarly the system testing approach is discussed and a method of wide generality is described in detail. The Electromagnetic Compatibility (EMC) tests commonly devised for a system based upon the 'black box' concept shall be formulated in a more general manner. The overall system hardening tests which are now carried out mainly on a qualitative basis shall be specified and performed on a quantitative one. NATO Furnished. (RH), This article is from 'The Design, Development and Testing of Complex Avionics Systems: Conference Proceedings Held at the Avionics Panel Symposium in Las Vegas, Nevada on 27 April-1 May 1987', AD-A198 666, p24-1 thru 24-10.

This paper describes a design tool called ECATE (Expert Consultant for Avionics System Transformation Exploitation) developed by the Avionics System and Equipment Group of Aeritalia. ECATE, rapidly prototyping different alternatives, helps the designer in establishing the information flow architecture of the avionics system, that is the organization of the internal data handling. The tool provides the user with an interface to assist him in describing the avionics from the point of view of the data handling, and presents the results in a suitable format; it performs consistency checks and advices the user on possible architectural problems by means of the expert system techniques. The paper contains also some indications on the development environment of the tool and how it works in a consulting session. Some examples give an idea of the result that can be obtained. Conclusion is that not only the tool is valuable for the information flow architecture design but also it shows that the use of the knowledge engineering and the Artificial Intelligence techniques can be effective to meet the problems arising when complex systems, not only avionics, are involved. NATO Furnished. (rh)

The conventional process of a new aircraft design and development is based on sequential analysis and test cycles. Using an integrated CAE-CAD-CAM technique it is possible to increase the depth of the different configurations analysis, to reduce the cycle time and even the number of cycles required, and to achieve optimised design, thereby improving the product, shortening the overall development time, and reducing development costs. The capability of CAD systems to manipulate 3-D geometric models utilizing data base of standard components, allows the integrated development of aerodynamic and structural configurations, and of systems layout. A computerised mock-up developed at CAD allows to converge on a unique mathematical model different disciplines, making easier integrations between structures and equipments. The CAD total data base integrated with analysis and manufacturing permits direct data transfer from engineering to manufacturing (CAM) and in addition makes faster and cheaper the embodiment of modifications during the development phase., This article is from 'Flight Vehicle Development Time and Cost Reduction: Conference Proceedings Held at the Flight Mechanics Panel Symposium in Toulouse (France) on 11-14 May 1987', AD-A198 663, p9-1 thru 9-9.

The aim of this paper is to show what could be the kind of joints that would reduce the electrical resistance when a carbon fiber reinforce structure has to be jointed with an aluminum part. Assembly of specimens has been considered in fixed and removable configurations. Carbon fiber reinforced plastic F263-T300 Fabric 3K70PW; and Aluminum alloy 2-24 - T3. New difficulties are arising during the design of CFRP parts in comparison with aluminum ones. The main problem with be to verify the composite structure behaviour from the electrical point of view. It will be necessary to consider how the environment will affect the structures made of composite material. Events such as lightning strike can have more dangerous effects on CFRP than on metallic parts. (SDW), This article is from 'Behaviour and Analysis of Mechanically Fastened Joints in Composite Structures', AD-A199 171, p10-1 - 10-11.

Extensive autopilot system performance evaluations have been conducted on TORNADO Prototype 05 and 09. Several problems affecting equipments, control laws, system integration (hardware and software) were discovered and studied. The activity took advantage from various computing and simulation facilities to analyse data from fast data transmission lines and an avionic integration rig with real-time closed-loop simulation capability. Lessons learnt are reported. Trends for next trials conduct are discussed outlining engineering activities and ground facilities needs i.e. simulation and system rig, required to support flight testing of prototype avionic systems., This article is from the Proceedings of the Flight Mechanics Panel Symposium Held in Lisbon, Portugal on 2-5 Apr 84, AD-A147 625, p11-1 - 11-17.

Within the scope of a new program for a single engine combat aircraft, a complete afterbody model has been designed and tested in a transonic wind tunnel to integrate the experimental results obtained from the unpowered models. In addition to the aims of the traditional afterbody models, i.e. engine jet effect on aerodynamics, the model has been designed with the potential capability to investigate the tailplane effectiveness and the effects of the secondary jet outlets, tail fairings, excrescences, aerials etc. With respect to these purposes, the present paper deals with the general arrangement of the model, describing briefly the first phase tests carried out in the ARA transonic wind tunnel. It is necessary that, in order to obtain reliable results in terms of afterbody drag, there be an accurate sealing between the fixed and the weighted parts with the minimum mechanical interference., This article is from 'Wind Tunnels and Testing Techniques,' AD-A143 674, p26-1-26-15.

The operational conditions of two spacecrafts performing a rendez-vous in geostationary orbit are given with the relative motion equation and the relevant control law. The concept of position, velocity and attitude measurement of the chaser vehicle with respect to the target one is given in order to allow the evaluation of the measurement errors. Simulations show the effect of the errors sources on the flight path of the approaching vehicle and point out the necessity of a good matching between the sensor accuracy and the minimum impulse level of the actuation system. (Author), This article is from 'Conference Proceedings on Guidance and Control Techniques for Advanced Space Vehicles (37th) Held at Florence, Italy on 27-30 September 1983,' AD-A141 969, p13-1 - 13-13.

This paper illustrates an operational analysis tool to assist in understanding complex system features. Application to the design and development of the avionic system of a tactical fighter is described with special regard to critical factors affecting the system development or part of it. It is pointed out that the described tool is not to be used to design or develop the system, which requires much more complex activities, but it is a possible useful way to summarize and present the results of the operations research in order to trim the project in the right direction. Additional effort toward system optimization, configuration definition and development trade-offs can be made by means of the marginal substitution rate factors. Application of the above tools and techniques has been and is currently being done for systems similar to the examples such as the development of the avionic system of AM-X aircraft., This article is from 'Advanced Concepts for Avionics/Weapon System Design, Development and Integration: Conference Proceedings of the Avionics Panel Symposium (45th) Held at Ottawa, Canada on 18-22 April 1983,' AD-A138 600, p29-1-29-13.

During production of advanced composite structural parts, because of material manufacturing process anomalies, some typical defects, such a porosity and/or delaminations, may become embodied into the final product. In order to improve the accept/reject criteria for typical defects, AERITALIA's G.V.C. Laboratories have carried out a static/fatigue test program on specimens in which various porosity levels were simulated. Further, an attempt has been made to correlate mechanical performance with the ultrasonic energy absorption measures., This article is from 'Characterization, Analysis and Significance of Defects in Composite Materials. Conference Proceedings: Meeting of the Structures and Materials Panel (56th) Held in London on 12-14 April 1983, AD-A134 058. p9-1-9-7.

During the interaction of a high-power laser beam with a material surface many fluid-dynamical phenomena arise. The produced flow field interacts with the beam and affects the thermal coupling between the laser energy and the target metal. In this paper the fluid-dynamical aspects of these phenomena are discussed and new experimental results are illustrated. The experiments have been performed in conditions of interest for industrial laser processes with a 15-kW CWC)2 laser. The developing and the motion of bright clouds ignited from metal targets at incident laser power up to 11.6 kW, using an f/18 focusing system, have been studied by high speed photographic records. The properties of the cloud have been examined by spectroscopic analysis and absorption measurements., This article is from 'Proceedings of the International Symposium on Shock Tubes and Waves (13th), Niagara Falls, July 6-9, 1981,' AD-A122 200.

A study was made of the effect of small amounts of impurities on recrystallization of Fe and related effects of recovery and grain growth. Methods of preparation of high purity Fe were studied. Some pure Fe specimens were carburized at 700 C with increasing amounts of C added to the H2. These, together with other specimens of Fe of different purity, were cold worked in different amounts and the recovery and recrystallization were followed by hardness, micrographs and x rays. In pure Fe, recovery effects and recrystallization were observed much before the less pure specimens. The effect of C appears small in comparison with the effects of some substitutional elements. Preliminary measurements of grain boundary internal friction of pure Fe with different C content were performed. Displacement of the grain boundary peak was consistent with the recrystallization temperature.

A detailed description is given of an apparatus for thermoluminescence (above room temperature i.e. up to about 350 C), having the following peculiar features: the linear rate of warming is obtained through a cam-actuated Variac transformer; the light detection makes use of phase rectification; the apparatus is provided with a special furnace for recording glow current curves. The possibility of rendering flat the spectral response of the photomultiplier between 2000 and 6000 A through a composite filter is investigated and the method of calculating such a filter is developed. The performances of the apparatus were satisfactory.

The kinetics of the decay of the Frozen Polarization (FP) shown by an Electroluminescent Cell (ELC) after excitation which a suitable waveform of electrical potential has been studied as a function of temperature between +7 C and +42.5 C. The order of the kinetics was evaluated as well as the thermal activation energy, which turned out to be around 2.5 EV. This figure corresponds closely to the ionization energy of Cu(+) impurities in ZnS(Cu) phosphor. The kinetics of the decay of the amount of light which an ELC gives out under excitation by a single linear voltage transient retarded on variable amounts with respect to a previous excitation were investigated. The latter consisted of a train of linear transients long enough to saturate the cell. The phenomenon has been followed from -44.5 C to +47.5 C, and again an activation energy has been found of roughly 1.5 ev. The connection between these two experiments and its possible implications are briefly discussed to cast some light on the mechanism of barrier injection of carriers in EL phosphors.

A short review of the literature on electroluminescence (EL) is given. The analysis is limited to phosphors of (activated) ZnS type and to intrinsic EL, i.e., EL excited in condenser type cells, filled with powder phosphors embedded inA GOOD DIELECTRIC MEDIUM. A new technique, suggested for studying the behaviour of the EL, consists of applying to the cells single transients of voltage (respectively rising or falling) with a constant rate of variation vs time. The circuits used for this technique are described, as well as the preliminary results obtained with commercial EL cells. These results are of a good quantitative character.

Continuing the research work on the effect of small amounts of substitutional transition elements on recrystallization, recovery and grain boundary relaxation in iron, data obtained for a new set of iron alloys containing Co, Mn, Ga and Ge (contents ranging from 40 to 1075 atoms per million) are reported. A discussion concerning also the results previously obtained (for alloys with Ti, V, Co, Ni, Cu) is given.

Experiments are reported concerning the photoelectroluminescence emission in ZnS. A well-defined equation has been obtained about the brightness voltage dependence; it is justified through a simple kinetic investigation based on a model for the electroluminescent process already reported. Evidence is also gained against the Fischer model. An apparatus to perform the measurements of fluorescence spectra during the decay of the photoluminescent emission is described. It succeeds in providing a digital recording of the spectra for times ranging between 10 ms to several seconds. (Author)

Two experiments have been performed, concerning the interpretation of the EL process mechanism. The first deals with the behavior of the EL output at liquid helium temperature. The small decrement of the luminescence at 4.2K, demonstrates that the thermal regeneration of electron-hole pairs, invoked in the Fisher model, does not occur in practice. The second experiment, performed by striking the EL comets with an U.V. light spot, shows that a transport of carriers takes place from the comet head towards the tail. Even this experiment disagrees with the Fisher model. On the contrary, both the experiments well support an alternative EL model already proposed by the writers. (Author)

The light distribution along a single EL line is investigated as a function of frequency and amplitude of the applied voltage. It is found that the brightness decreases from the head towards the tail of the comet following the exponential law: B = B(o)e to the minus x/L power; where L, being almost constant versus the frequency, depends linearly on the amplitude of the exciting voltage. Theoretical considerations, founded on a model previously advanced, are developed which show how these new experimental results can be readily accounted for. (Author)

Experiments have been performed on the Thermoluminescence (TL) due to Electroluminescent (EL) excitation of ZnS(Cu) single crystals. Two major glow peaks are found respectively at 35 and 100K, the first being characteristic of EL excitation. The measured activation energies of these glow peaks turn out to be 0.00361 eV and 0.0931 eV and the kinetics order approximately 0.5 and 1. The integrated light intensity of the first glow peak overcomes that of a single EL brightness wave at the same voltage by a factor of about 10,000. With reference to the EL model previously put forward by us these experimental results can be accounted for satisfactorily. The first peak in fact appears due to electrons trapped at the broken bonds lying along the EL defect and the second peak is produced by electrons scattered during the direct bias injection and successively trapped in the bulk ZnS. (Author)

Contents: Varley mechanism for defect formation in alkali halides; Defect formation in alkali halides by ionizing radiation; Creation of defects in alkali halides by ionizing radiation; Thermoluminescence of X-colored alkali-halide crystals; Correlation between current and luminescence glow-curves of X-colored alkali-halide crystals; Effect of X-ray coloring on additively colored alkali halides; Thermoluminescence and optical absorption spectra of 'imperfect' alkali halides X-rayed at low temperature; Pressure induced thermoluminescence; Effect of temperature on color centers in alkaline earth fluorides; Production of color centers in apatite halophosphates by shortwave ultraviolet radiation; Dichroic color centers in calcium fluoro-phosphate; Polarization of F and M-centers; Thermal equilibrium between F and M-Centers in potassium chloride; Host sensitized luminescence in the alkali halides; Luminescence of alkali halides under ionizing radiation; Experiments on the electroluminescence of ZnS single crystals; Gudden-Pohl effect in single crystals of zinc sulphide; Defect centers and luminescence in diamond; and Etch pits on electroluminescent zinc sulfide crystallites.

A series of experiments on the electroluminescence (EL) featured by AgCl at liquid nitrogen temperature. The specimens used were single crystals of unintentionally doped or Mn doped AgCl, either as grown and cut, annealed, plastically deformed, or previously irradiated with UV light. The current vs voltage and the brightness vs voltage characteristics were investigated, as well as the topography of the light pattern at low magnification. The results obtained, described in a detailed way in the text, confirm and extend the little already known about the EL of silver halides. Definite differences are found with respect to the case of the Destriau effect exhibited by ZnS electroluminors. (Author)

It was found that the frozen polarization (FP) of ZnS(Cu) bears no relationship to the electroluminescence of the same material. This result is obtained directly by studying the effect of the crystal surface conditions on the temporal behavior of FP. Indirect evidences are also reported about the effect of illumination on FP. It is concluded that FP is, on the contrary, probably imputable to traps arising at the interrupted tethraedral bonds on the crystal surface. (Author)

A novel model of the Destriau effect (ac EL in ZnS(Cu)) is presented that looks capable of interpreting in a consistent way all the principal experimental features of EL. This result is obtained through consideration of the semiconducting properties of definite partial dislocations bordering stacking faults in hexagonal structure basal planes. After a thorough critical survey of existing theories, the crystal defect spoken of is described and its properties illustrated, showing how they lead to the occurrence of the Destriau effect. (Author)

The present note describes the construction of the electronics to be used for recording time-dependent spectra of electroluminescent crystals. The fundamentals of the digital method employed to measure the distribution of delay between the excitation and the emission are briefly outlined pointing out its interest for our problems. The electronic circuitry is then described and some preliminary experiments are reported, that demonstrate the performance of the whole setup. (Author), See also Part B, AD-662 625.

The paper discusses results of measurements about the time dependence of the monochromatic components of the light emitted by Electroluminescent ZnS single crystals, Cu activated, subjected to a sinusoidal voltage. The light was analyzed with a spectrometer and its time dependence was digitally recorded using a time-to-pulse height conversion technique. The light of two crystals, one (labelled A) exhibiting blue and green EL, the second (labelled B) exhibiting blue, (very weak green) and red EL, was analyzed at 77 degrees K. Both with respect to the exciting voltage and to each other the spectral components of crystals A and B appear nearly 'in phase', although small time lags, of the order of 0.1 period, different for each component, were actually measured. Between the alternances of the exciting voltage the light does not fall to zero, the relative importance of the continuous light pedestal being different for the various spectral bands. No obvious relationship, however, with the decay times has been found. These results are compared with the few data available from the literature and their relevance as to the mechanism of the EL is briefly discussed. (Author), See also Part B, AD-662 625.

A complete description is given of a first prototype of a SMODOS instrument, namely of its optical as well as electronic components. The project criteria are thoroughly discussed and some performances are shown, practically demonstrating the power of the method.

The occurrence of a large aging effect in Cu-doped electroluminescent ZnS single crystals is demonstrated. It is suggested that the ac electroluminescent behavior of this material is influenced by reprecipitation of the Cu-rich phase within the host matrix. (Author), Pub. in Physics Letters v13 n3 p197-8 Dec 1 1964 (Copies available only to DDC users).

Several subjects which have been or are being investigated at the laboratory are surveyed. First, alkali halide thermoluminescence above room temperature: a model is proposed, using a 2nd order kinetics, that accounts well for a number of experimental results rather poorly explained by previous theories. Experiments are then mentioned on intrinsic electroluminescence of ZnS specimens, undergoing linear voltage transients. The results are compared with those predictable on the basis of a mathematical development of Zalm's theory. Electron microscopy studies of tracks of fission products in mica are then quoted, to end with a mention of experiments on surface electrical conductivity in metals. (Author), Pub. in Fisica dello Stato Solido: Convegno Indetto dalla Societa Lombarda di Fisica, Pavia, 16-18 Luglio 1962 Text in Italian (Copies available only to DDC users).

A technique is described for exciting electroluminescence by means of single transients having a constant derivative in time. Results obtained by the use of the method on ZnS commercial cells of the condenser type are reported., Pub. in mono. Luminescence of Organic and Inorganic Materials, New York, p605-12 1962 (Copies available only to DDC users).