Detection of low-velocity impact-induced delaminations in composite laminates using Auto-Regressive models

In this paper, the detection of delaminations in carbon-fiber-reinforced-plastic (CFRP) laminate plates induced by low-velocity impacts (LVI) is investigated by means of Auto-Regressive (AR) models obtained from the time histories of the acquired responses of the composite specimens. A couple of piezoelectric patches for actuation and sensing purposes are employed. The proposed structural health monitoring (SHM) routine begins with the selection of the suitable locations of the piezoelectric transducers via the numerical analysis of the curvature mode shapes of the CFRP plates. The normalized data recorded for the undamaged plate configuration are then analyzed to obtain the most suitable AR model using five techniques based on the Akaike Information Criterion (AIC), the Akaike Final Prediction Error (FPE), the Partial Autocorrelation Function (PAF), the Root Mean Squared (RMS) of the AR residuals for different order p, and the Singular Value Decomposition (SVD). Linear Discriminant Analysis (LDA) is then applied on the AR model parameters to enhance the performance of the proposed delamination identification routine. Results show the effectiveness of the developed procedure when a reduced number of sensors is available

The structure of problem-solving knowledge and the structure of organisations

This work presents a model of organisational problem solving able to account for the relationships between problem complexity, tasks decentralilzation and problem solving efficiency. Whenever problem solving requires the coordination of a multiplicity of interdependent elements, the varying degrees of decentralization of cognitive and operational tasks shape the solution which can be generated, tested and selected. Suboptimality and path-dependence are shown to be ubiquitous features of organisational problem solving. At the same time, the model allows a precise exploration of the possible trade-offs between decompostion patterns and search efficiency involved in different organisational architectures.-

Thermal conductivity of lipidic emulsions and its use for production and quality control

Thermal conductivity of lipidic emulsions has been experimentally determined by the probe method. To this purpose a special probe has been designed and built in laboratory, with small diameter (0.6 mm) and a high length to diameter ratio (100). The temperature sensor of the probe (type T thermocouple) and the heater (Pt wire) were properly calibrated. Moreover, the probe performance has been tested by means of a pure liquid (glycerin) having well known thermal conductivity by literature. Differences of about 1.5% at ambient temperature in thermal conductivity values between literature and experiments were found. On lipidic emulsions first thermal conductivity has been measured in the temperature range 1040°C, second the same property as a function of time at constant temperature (40°C), then the values after freezing at –15°C and reheating at 20 °C; and last the kinetics of degeneration. Results show a significant difference between thermal conductivity values of a new emulsion (0.51 W/m K), compared with the creamed one (0.62 W/m K), and the decayed one (0.68 W/m K ). It has also put into evidence why the frozen emulsion cannot be used for intravenous injection, i.e. viscosity increases because of breaking of the oil particles. Finally information about the kinetics of the degeneration process have been obtained. The uncertainty resulting from the calibration and tests justifies the possible use of the measurement technique for process control of production, and also for quality control in the clinical practice

Circadian and ultradian rhythms in locomotory activity of inbred strains of mice

In this study we recorded locomotor activity of two inbred of mice (B6 and C) in two photoperiod conditions (LD 12:12 and DD) to characterize behavioural parameters of the endogenous rhythms of locomotor activity with particular attention to the ultradian rhythms. Literature reveals discordant data for these parameters, both for animals belonging to the same strain and to those in the same laboratory or monitored in the same conditions. Our results show that C strain has a shorter and unstable endogenous circadian period, while B6 strain has a longer and stable endogenous rhythm. In our study, B6 showed a longer and stable period than C, so we can confirm the presence of a genetic component underlying this trait. Ultradian rhythms are expressed independently of either the photoperiod or the circadian rhythm. There are no strain-dependent differences in the periods of 12, 8 and 4 h. The situation was different for the length of the ultradian period in the range 1-8 h and for the weighted power in the ranges 480-300 and 300-100 min, for which there were differences between photoperiods and strains

Validation of a microwave radar system for the monitoring of locomotor activity in mice

BACKGROUND: The general or spontaneous motor activity of animals is a useful parameter in chronobiology. Modified motion detectors can be used to monitor locomotor activity rhythms. We modified a commercial microwave-based detection device and validated the device by recording circadian and ultradian rhythms. METHODS: Movements were detected by microwave radar based on the Doppler effect. The equipment was designed to detect and record simultaneously 12 animals in separate cages. Radars were positioned at the bottom of aluminium bulkheads. Animal cages were positioned above the bulkheads. The radars were connected to a computer through a digital I/O board. RESULTS: The apparatus was evaluated by several tests. The first test showed the ability of the apparatus to detect the exact frequency of the standard moving object. The second test demonstrated the stability over time of the sensitivity of the radars. The third was performed by simultaneous observations of video-recording of a mouse and radar signals. We found that the radars are particularly sensitive to activities that involve a displacement of the whole body, as compared to movement of only a part of the body. In the fourth test, we recorded the locomotor activity of Balb/c mice. The results were in agreement with published studies. CONCLUSION: Radar detectors can provide automatic monitoring of an animal's locomotor activity in its home cage without perturbing the pattern of its normal behaviour or initiating the spurt of exploration occasioned by transfer to a novel environment. Recording inside breeding cages enables long-term studies with uninterrupted monitoring. The use of electromagnetic waves allows contactless detection and freedom from interference of external stimuli

Using Anisotropic Diffusion for Coherence Estimation

In this paper we will present a new coherence estimation technique for SAR interferometry products that adapts the estimation window size and shape during processing. This is of particular interest for sensors with medium spatial resolution, like the ASAR WS mode, where the estimator shall cope with the spatial variability of the targets in the imaged area. This method is designed to remove low coherence magnitude bias while keeping a good spatial resolution. Finally, this new approach will be compared to an existing algorithm for quantifying resulting quality improvement

An infra-red beam device for the study of the motor activity rhythms on groundwater mysidacea

ItL’attività motoria o locomotoria è un parametro utile per comprendere il funzionamento degli orologi biologici. Gli animali cavernicoli rappresentano un eccellente modello per gli studi cronobiologici oltre che per comprendere l’evoluzione e l’adattamento alla vita sotterranea.Le ricerche in ambito cronobiologico richiedono spesso monitoraggi molto lunghi per i quali è necessario ricorrere all’utilizzo di sistemi automatici. L’obbiettivo primario del presente lavoro consiste nel testare, con animali vivi, il prototipo di un apparato elettronico ad infrarossi appositamente costruito per il monitoraggio dell’attività motoria di animali acquatici di piccole dimensioni. La specie utilizzata in questa ricerca è un misidaceo, Spelaeomysis bottazzii Caroli 1924, proveniente dalla Grotta di San Isidoro (Nardò – LE, Pu/507). La registrazione dell’attività motoria ha riguardato animali mantenuti singolarmente in celle di coltura da 30 ml (5x3x2 cm). L’attività motoria è stata rilevata con un sistema di 9 barriere a luce infrorossa (ciascuna barriera composta da una sorgente e un sensore alle sue estremità). I sensori erano collegati ad un circuito elettronico che inviava i segnali ad un personal computer che a sua volta li archiviava. È stata eseguita un’analisi qualitativa dell’attività motoria dei singoli animali, rappresentandola graficamente per mezzo di attogrammi. Inoltre è stata eseguita un’ analisi quantitativa esplorativa di questi primi dati sull’attività motoria dei misidacei. A tal fine tutte le serie temporali sono state analizzate applicando la trasformata discreta di Fourier (DFT). Sono state eseguite registrazioni per un totale di 20 giorni, 24 ore su 24 (12 gg il primo animale, 4 gg il secondo ed il terzo animale). Durante tale periodo non sono stati riportati problemi di eccessivo surriscaldamento dell’acqua, la componente elettronica (in particolare quella optoelettronica) si è rivelata altamente sensibile e non ha mostrato segni di usura dovuti alle condizioni di utilizzo. Gli animali sono rimasti vivi sino alla conclusione dell’esperimento. L’ispezione visiva degli attogrammi ha evidenziato una continua e costante rilevazione dell’attività locomotoria dei misidacei. L’analisi cronobiologia si è concentrata sul calcolo della lunghezza del periodo circadiano in free-running, trovando un periodo medio di 24,7 h. La DFT ha rilevato la presenza di un picco a circa 24 h in tutte le registrazioni esaminate, evidenziando inoltre una bassa potenza spettrale.Oltre al ritmo circadiano, in tutte le registrazioni ricorrevano ritmi ultradiani nell’attività motoria. Nonostante le repliche sperimentali non siano sufficienti a giustificare conclusioni circa i ritmi dell’attività motoria di Speleomysis bottazzii, i ritmi individuati e la loro differente intensità, testimoniano di un incoraggiante funzionamento dell’apparato progettato.EnLocomotor activity and cave animals represent excellent models for study of biological clocks. An infrared-based detection device for recording motor activity has been tested on the stigobitic Spelaeomysis bottazzii Caroli, 1924 (Crustacea: Mysidacea). The individual activity of mysidaceans was monitored in continuous darkness. Data were analyzed by a DFT and chi-square periodogram. The apparatus was able to read rhythms of activity, in particular a lower circadian rhythm and some ultradian ones