P. Placidi

Automated defect detection in uniform and structured fabrics using Gabor filters and PCA

This paper describes an algorithm for texture defect detection in uniform and structured fabrics, which has been tested on the TILDA image database. The proposed approach is structured in a feature extraction phase, which relies on a complex symmetric Gabor filter bank and Principal Component Analysis (PCA), and on a defect identification phase, which is based on the Euclidean norm of features and on the comparison with fabric type specific parameters. Our analysis is performed on a patch basis, instead of considering single pixels. The performance has been evaluated with uniformly textured fabrics and fabrics with visible texture and grid-like structures, using as reference defect locations identified by human observers. The results show that our algorithm outperforms previous approaches in most cases, achieving a detection rate of 98.8% and a false alarm rate as low as 0.20-0.37%, whereas for heavily structured yarns misdetection rate can be as low as 5%.

A System for the Dynamic Control and Thermal Characterization of Ultra Low Power Gas Sensors

This paper describes a system for the simultaneous dynamic control and thermal characterization of the heating and cooling phases of an ultralow-power (ULP) micromachined sensor, featuring thermal characteristics that are quite similar to those of innovative ULP semiconducting metal-oxide gas sensors. A pulsewidth-modulated (PWM) excitation system has been realized using a microcontroller featuring an ARM7 core to characterize the thermal behavior of a device formed by a Pt microheater and a Pt temperature sensor, over an insulating membrane. Three operating modes, i.e., constant target heater resistance, constant heating power, and cooling phase monitoring, were implemented. Objectives of the research were to analyze the relation between the time period and duty cycle of the PWM signal and the operating temperature of such ULP micromachined systems, to observe the thermal time constants of the device during the heating and cooling phases, and to measure the total thermal conductance. Experiments indicated that an approximately constant heater temperature in the constant target heater resistance regime (i.e., after the initial thermal transient due to the heating algorithm) can only be obtained if the time period of the heating signal is smaller than 50 μs, i.e., much faster than the time constant of the device. Constant power experiments show quantitatively a unique time constant τ for both the heater and the temperature sensor (T-sensor) in the heating phase (with a known applied power) and the cooling phase (with zero power). This time constant decreases during heating in a range of 2.3-2 ms as a function of an increasing temperature rise ΔT between the ambient and the operating temperature. Moreover, we observed that, in the chosen operating temperature range, the thermal conductance is a linear function of ΔT. Finally, repeatability of experimental results was assessed by guaranteeing that the standard deviation of the controlled temperature was within ±5.5°C in worst-case conditions.

An enhanced approach to numerical modeling of heavily irradiated silicon devices

Abstract In this paper we discuss an enhanced approach to the analysis of radiation-damaged silicon devices, with reference to numerical modelling implemented in a general-purpose device simulator. In particular, the emission and capture mechanism of deep levels are accounted for by means of Shockley–Read–Hall theory and shallow-level sensitivity to radiation is considered by means of a donor removal model. The effects produced by regions containing very high defect concentrations (referred to as “clusters”) are considered by calculating the direct charge exchange between two deep levels. The resulting analysis technique has been validated and calibrated by means of comparison with experimental measurements carried out on irradiated samples. The model is shown to provide comprehensive and accurate results for several radiation damage phenomena.

A Programmable Interface Circuit for an Ultralow Power Gas Sensor

Abstract-An electronic system based on a microcontroller architecture, devoted to interfacing a three-terminal, ultralow power (ULP) Metal OXide (MOX) gas sensor is presented. The sensor features a novel three-terminal configuration where the microheater is not galvanically isolated with respect to the MOX sensor. The system provides both control of the operating temperature and management of the acquired data. A Pulse Width Modulation (PWM) signal with variable duty cycle is used to provide power to the heating resistor in order to set the desired operating temperature. The heating resistance value is measured in the range (100-300) Ω with a relative error of less than 1%. The circuit devoted to measuring the gas concentration is based on a logarithmic amplifier which measures the current flowing in the sensing layer of the sensor. The measurand range is 30 nA to 60 mA and the relative error of the measured current is less than 0.6%. The data acquisition system was successfully tested by acquiring data of a three-terminal ULP gas sensor located in an automatically controlled environmental chamber under benzene and NO2 flow.

A simple interface circuit for micromachined gas sensors

Abstract This paper describes a microcontroller-based interface circuit for chemoresistive metal-oxide gas sensor dedicated to environmental pollution detection. The circuit controls the sensor operating temperature, measures the sensing layer resistance, offering also a user-friendly interface. The main system features are: wide dynamic measurement range, self-calibration capability, built-in RS-232 interface and two different methodologies of data acquisition, namely constant and pulsed temperature modes.

Device simulations of silicon detectors: a design perspective

Device simulation allows for accurate analysis of device behavior, accounting for several physical details that cannot easily be taken into account within compact, equivalent-circuit models. This is especially true for some issues typical of the design of silicon radiation detectors, where silicon properties are exploited in a non-conventional way and radiation damage raises severe reliability concerns. In this paper, a couple of significant applications of device simulation to the investigation and design of advanced solid-state radiation sensors are presented. More specifically, (i) radiation damage influence on detectors operating at cryogenic temperatures is successfully modeled and (ii) features of an innovative scheme for CMOS active pixel sensors are analyzed by means of mixed-mode simulation tools. From these examples, the usefulness and potentiality of advanced simulation techniques in the perspective of radiation detectors can be appreciated.

Solid anaerobic digestion batch with liquid digestate recirculation and wet anaerobic digestion of organic waste: Comparison of system performances and identification of microbial guilds

Solid anaerobic digestion batch (SADB) with liquid digestate recirculation and wet anaerobic digestion of organic waste were experimentally investigated. SADB was operated at an organic loading rate (OLR) of 4.55kgVS/m3day, generating about 252NL CH4/kgVS, whereas the wet digester was operated at an OLR of 0.9kgVS/m3day, generating about 320NL CH4/kgVS. The initial total volatile fatty acids concentrations for SADB and wet digestion were about 12,500mg/L and 4500mg/L, respectively. There were higher concentrations of ammonium and COD for the SADB compared to the wet one. The genomic analysis performed by high throughput sequencing returned a number of sequences for each sample ranging from 110,619 to 373,307. More than 93% were assigned to the Bacteria domain. Seven and nine major phyla were sequenced for the SADB and wet digestion, respectively, with Bacteroidetes, Firmicutes and Proteobacteria being the dominant phyla in both digesters. Taxonomic profiles suggested a methanogenic pathway characterized by a relevant syntrophic acetate-oxidizing metabolism mainly in the liquid digestate of the SADB. This result also confirms the benefits of liquid digestate recirculation for improving the efficiency of AD performed with high solids (>30%w/w) content.

CHIPIX65: Developments on a new generation pixel readout ASIC in CMOS 65 nm for HEP experiments

Pixel detectors at HL-LHC experiments or other future experiments are facing new challenges, especially in terms of unprecedented levels of radiation and particle flux. This paper describes the progress made by the CHIPIX65 project of INFN for the development of a new generation readout ASIC using CMOS 65 nm technology.

The RD53 Collaboration's SystemVerilog-UVM Simulation Framework and its General Applicability to Design of Advanced Pixel Readout Chips

The foreseen Phase 2 pixel upgrades at the LHC have very challenging requirements for the design of hybrid pixel readout chips. A versatile pixel simulation platform is as an essential development tool for the design, verification and optimization of both the system architecture and the pixel chip building blocks (Intellectual Properties, IPs). This work is focused on the implemented simulation and verification environment named VEPIX53, built using the SystemVerilog language and the Universal Verification Methodology (UVM) class library in the framework of the RD53 Collaboration. The environment supports pixel chips at different levels of description: its reusable components feature the generation of different classes of parameterized input hits to the pixel matrix, monitoring of pixel chip inputs and outputs, conformity checks between predicted and actual outputs and collection of statistics on system performance. The environment has been tested performing a study of shared architectures of the trigger latency buffering section of pixel chips. A fully shared architecture and a distributed one have been described at behavioral level and simulated; the resulting memory occupancy statistics and hit loss rates have subsequently been compared.

Use of a CMOS Image Sensor for an Active Personal Dosimeter in Interventional Radiology

Interventional radiologists and staff members, during all their professional activities, are frequently exposed to protracted and fractionated low doses of ionizing radiation. Due to skin tissues and peripheral blood irradiation, these exposures can result in deterministic effects (radiodermatitis, aged skin, and hand depilation) or stochastic ones (skin and non-solid cancer incidence). The authors present a novel approach to perform online monitoring of the staff during their interventions by using a device based on an Active Pixel Sensor. The performance of the sensor as an X-ray radiation detector has been evaluated with a proper experimental setup: the number of photons and the generated charge have been assessed as dosimetric observables from the frames acquired by the sensor using a two-threshold clustering algorithm, the efficiency of which has been evaluated as well. The correlation of these observables with passive dosimeter dose measurements has been analyzed: a good linearity has been demonstrated, and the response difference between pulsed and continuous operational modes is reduced to less than 10%, marking a distinct improvement with respect to commercial Active Personal Dosimeters.