Laura Fabbiano

Improved Static Testing of A/D Converters for DC Measurements

A new method is presented for the calibration and the linearity testing of analog-to-digital converters (ADCs) and dc digital instruments, such as digital voltmeters (DVMs). The test is truly static, because it uses only dc voltages with a small superimposed noise (dithering). It is much faster than that described in the IEEE Standard 1057/94 since it uses a minimal number of test signals and acquired samples in a theoretically nearly optimal manner, i.e., maximum-likelihood estimation. In addition, contrary to the test described in the IEEE Standard 1241/00, it allows offline measurements and testing of stand-alone instruments, such as DVMs. Another advantage of the proposed method is that the resolution requirements for the source of test signals are relaxed. After a review of the state of the art, this paper provides the mathematical derivation of the employed estimator. Simulations, theoretical analyses, and experimental results are also provided to illustrate the performances of the proposed test method.

Image-based detection of Kayser-Fleischer ring in patient with Wilson Disease

In the paper the authors propose an image processing algorithm for detection of Kayser-Fleischer ring in eye cornea. This is a common symptom of a rare genetic disorder known as Wilson Disease. This pathology is cause of a malfunction in the copper excretion from the organism. So copper accumulates in tissues being responsible of oxidative processes in the organs affected. Copper deposit in the cornea is visible as a golden-brown, sometimes orange or greyish, pigmentation called Kayser-Fleischer ring. So it is considered a diagnostic sign of Wilson disease more than ever in individuals with neurological disorders. The proposed algorithm is based on an image processing approach. In detail, eye image is analyzed by means of a segmentation algorithm to detect the Kayser-Fleischer ring. The proposed screening method is non-invasive and automated. The innovative diagnostic tool aims to improve accuracy of actual methods used in practice. So the described technique reduces possible interpretation errors and assists doctor to diagnose the pathology.

Ocular Biometric Measurements to Diagnose Neurological Disorders Due to Wilson Disease

Wilson disease is a pathology because of a gene mutation causing malfunction in the copper excretion from the organism. Therefore, copper accumulation in the body gives rise to oxidative processes. Hence, this rare disease causes several disorders affecting tissues and organs. Neurological disorders lead to copper accumulation in the brain. Approximately 95% of individuals with neurological/psychiatric disorders show a visible symptom in their eyes known as Kayser-Fleischer ring. It is a golden-brown, sometimes orange or greyish, ring because of copper deposit in the cornea. In the medical screening, it is considered as a diagnostic sign of Wilson disease more than ever in individuals with neurological problems. The authors propose an innovative technique based on ocular biometric measurements to diagnose the pathology and the origin of a neurological disorder. An image processing algorithm detects the Kayser-Fleischer ring in the eye cornea through segmentation. Subsequently, biometric measurements provide further information on the severity level of pathology. The aim is to provide a non-invasive diagnostic technique to improve the accuracy of the current methods used in practice and to reduce the possible interpretation errors.

Maximum likelihood estimation for linearity testing of ADCs stimulated by known constant signals

A maximum likelihood (ML) estimator is derived for the problem of measuring the code transition levels of an analog-to-digital converter (ADC). The proposed method is intended to test the linearity of the ADC in the static regime, using only constant test signals, except for a small amount of additive noise. The measurement data are employed in a nearly optimal manner, due to the statistical properties of the ML estimator, which are thoroughly examined. The reported analysis allows the design of the test under a given uncertainty constraint.

Velocity–Moisture Relationships for Sandy Soils: Experimental Results and Data Analysis

Many techniques have been proposed in recent years for in situ soil characterization, and among them, acoustic methods have been revealed to be particularly promising. These methods are based on measurements of the propagation velocities of seismic, sonic, and ultrasonic waves. However, in granular and porous mediums, velocities depend on the state of the saturation of the soil in a complex and not yet fully understood way. In this paper, a refined mathematical model to account for the effects of many soil properties such as porosity, bulk modulus, and pressure on acoustic wave velocity is proposed and investigated. The model has been validated by an experimental comparison between the measured and calculated values of velocities, using a kind of sand of known characteristics. A custom measurement system has been developed and realized for this purpose. The proposed model has potential applications in various areas, including geothermal resource evaluation, petroleum exploration, environmental protection, and archaeological and cultural site protection.

Design and Development of a sensor prototype for Soil Moisture Measurement: First Experimental Results

In this paper the design and the development of an innovative soil moisture sensor for agricultural applications is presented; also the first experimental results are illustrated and compared with those deriving by the underlying theory. The basic idea is to excite the soil with seismic waves (both compressional and shear ones) and to measure their velocity of propagation using a transmitter and a receiver that are separated by a known distance. The first encouraging experimental results here presented are obtained using the cross-correlation between the transmitted and the received signal; however repeated measures show a troublesome scattering around the theoretical values. In depth analysis has shown that this scattering is mainly due to the presence of interfering background noise; the authors are currently working to improve the experimental setup to guarantee better results.

Fluid flow measurements by means of vibration monitoring

The achievement of accurate fluid flow measurements is fundamental whenever the control and the monitoring of certain physical quantities governing an industrial process are required. In that case, non-intrusive devices are preferable, but these are often more sophisticated and expensive than those which are more common (such as nozzles, diaphrams, Coriolis flowmeters and so on). In this paper, a novel, non-intrusive, simple and inexpensive methodology is presented to measure the fluid flow rate (in a turbulent regime) whose physical principle is based on the acquisition of transversal vibrational signals induced by the fluid itself onto the pipe walls it is flowing through. Such a principle of operation would permit the use of micro-accelerometers capable of acquiring and transmitting the signals, even by means of wireless technology, to a control room for the monitoring of the process under control. A possible application (whose feasibility will be investigated by the authors in a further study) of this introduced technology is related to the employment of a net of micro-accelerometers to be installed on pipeline networks of aqueducts. This apparatus could lead to the faster and easier detection and location of possible leaks of fluid affecting the pipeline network with more affordable costs. The authors, who have previously proven the linear dependency of the acceleration harmonics amplitude on the flow rate, here discuss an experimental analysis of this functional relation with the variation in the physical properties of the pipe in terms of its diameter and constituent material, to find the eventual limits to the practical application of the measurement methodology.

A thermal energy balance model for hypotension prevention in hemodialysis

In the present paper, the authors propose a thermal energy balance model in order to prevent accidents in hemodialysis. Hemodialysis is the most common treatment for renal failure. It performs an extracorporeal blood wastes filtration taking the place of the malfunctioning kidney. Nevertheless this replacement therapy is cause of several side effects affecting the hemodynamic stability of patient. The authors focus attention on the hypotension accident. Thermal energy/heat exchanges between extracorporeal system and body might be cause of hypotension occurrence. Unfortunately, today poor importance is given to such aspects. A careful analysis of these issues has allowed authors to define a model for optimizing treatment procedures nowadays used in medical practice. In fact, most of the hemodialysis machines control automatically the dialysate solution temperature starting from peripheral body temperature measurements. Differently, the proposed approach is based on two control parameters: the predialysis patient core temperature and heat exchanges. Non-invasive temperature measurements of arterial and venous blood are obtained by estimating the thermal energy exchange. The aim of the present model is to guarantee a constant patient core temperature preventing intradialytic hypotension.

Observations on the worst case uncertainty

The paper discuss the computation of the worst case uncertainty (WCU) in common measurement problems. The usefulness of computing the WCU besides the standard uncertainty is illustrated. A set of equations to compute the WCU in almost all practical situations is presented. The application of the equations to real-world cases is shown.

An Innovative Strategy for Correctly Interpreting Simultaneous Acquisition of EEG Signals and FMRI Images

Cognitive event-related measurements of the human brain are performed by measuring electrical signals and electromagnetic fields (electroencephalography, EEG, and magnetoencephalography, MEG) and hemodynamic responses (measured by fMRI and PET). The EEG and MEG reflect synchronized electrical activity of neurons, and then show the same timescale as neurocognitive processes. The fMRI is related to the power consumption of groups of neurons and registers a signal on a timescale of several seconds. Unlike fMRI, MEG and EEG are not imaging methods. It is our opinion that the combination of MEG or EEG with the fMRI therefore would be very useful to reach a high resolution, both in time and space, of brain functions. It is not assured however that all measured events during an EEG acquisition and cognitive process-related produce measurable changes of the BOLD signal-and vice versa. In this paper, a new strategy of combining signals (electric and hemodynamic responses) simultaneously acquired from different clinical methodologies is performed and tested in order to produce more reliable information about brain activity. Two different algorithms are explored and compared via repeatability standard deviation estimations of fMRI images.