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Ultrasonic inspection is the go-to tool for many industrial NDE applications. Ultrasonic arrays have been employed in NDE since the 1980’s. However, with the rise of complex, computer-generated geometrical structures, the demand for arrays with the ability to conform to these structures is more pressing than ever before. The work here reports on the development of a truly flexible ultrasound array that allows previously uninspectable objects to be ultrasonically inspected.A novel, thin-film, piezoelectric material is deposited onto a flexible substrate using reactive sputtering of a metal-oxide-based alloy [1]. Additive manufacturing processes are then employed which allow for the mass manufacture of flexible arrays with consistent acoustic output and build quality, capable of operating in the region of 1-100 MHz. The arrays are subsequently demonstrated and tested on a variety of geometries such as moderate-diameter pipes and more complex test pieces. Moreover, these arrays are also demonstrated as permanently installed sensors, providing a solution to improved continuous monitoring with more information available to the industry.Data presented here includes sensitivity analysis and performance of a 64 element 15 MHz ultrasonic array. This was carried out using industry-standard NDE equipment, and common laboratory ultrasound apparatus. Preliminary testing has given strong indication that fully-flexible ultrasound arrays may be the future of industrial condition monitoring.Results demonstrated an array with effective performance following repeated flexion, indicating that they can withstand repeated conforming to test surfaces. The arrays tested achieved an average center frequency of 34 MHz, and average bandwidth at -6dB of 76%.

Cybersecurity is the second emergency in Europe just after the climate changes. Everyday most of the small, medium and big enterprises are under attack. This scenario requires, on one side, new security solutions protecting ICT systems against misbehaviors/malicious attacks and, on the other side, a continuous assurance process evaluating the system robustness against new threats. In this paper we present Moon Cloud, a Cloud PaaS solution providing customizable assurance based on compliance for ICT systems, including public and private cloud systems and IoT environments. We also present a concrete security assessment carried out in a real scenario.

The cloud computing paradigm entails a radical change in IT provisioning, which must be understood and correctly applied especially when security requirements are considered. Security requirements do not cover anymore just the application itself, but involve the whole cloud supply chain from the hosting infrastructure to the final applications. This scenario requires, on one side, new security mechanisms protecting the cloud against misbehaviors/malicious attacks and, on the other side, a continuous and adaptive assurance process evaluating the observed cloud security behavior against the expected one. In this paper, we focus on the evaluation of the security assurance of OpenStack, a major open source cloud infrastructure. We first define a security benchmark for OpenStack, inspired by Center for Internet Security (CIS) benchmark for cloud infrastructures. We then present a platform, called Moon Cloud, for cloud security assurance evaluation, showing an application of our benchmark and platform to the in-production OpenStack deployment of the University of Milan.

Ekici, Şule Önsel (Dogus Author) -- Conference full title: IEEE - IESM'2015 : proceedings of 2015 International Conference on Industrial Engineering and Systems Management (IESM) : October 21-23, 2015, Seville, Spain Risk identification and risk estimation are important stages of any risk management process. Existing research in Supply chain risk management has mainly focused on these two stages whereas risk evaluation has not been fully explored which is an equally significant stage involving evaluation of different risk mitigation strategies. The main purpose of this paper is to propose a method of evaluating different mitigation strategies through cost and benefit analysis. The proposed method introduces a unique concept of integrating cost and relative impact of different combinations of mitigation strategies within a network setting of interconnected risk triggers, risk factors and risk mitigation strategies. We have applied our method on a case study that was conducted in an aerospace supply chain. Our approach is useful in identifying an optimal combination of mitigation strategies against a given budget constraint. Furthermore, the model can also be used for determining such strategies in relation to a given level of risk exposure. We have incorporated NoisyOR function within the Bayesian Network model in order to reduce the complexity involved in eliciting a huge number of conditional probability values.

This paper aims to develop a position tracking controller for a micro-gripper's tip. The controller should be robust, able to compensate external disturbances and perform precise reference tracking under parameter variation and incertitudes. It becomes clear when considering the gripper's response on two different environments: air and vacuum. In this work, two models were identified based on experimental data, one for each case of study, and an extended high-gain observer controller based on output feedback is proposed. Simulations show that the controller, chosen to achieve a desired performance for the system in air, is able to maintain similar results in vacuum. The proposed setup was implemented in real-time for the system in air and simulated for vacuum.

Cloud users and service providers are increasingly concerned about the management of their data and the behavior of the applications they use/own once stored/deployed in the cloud. They therefore ask for enhanced assurance solutions, which partially mitigate the new risks and threats they are facing. Among existing solutions, certification has been widely adopted as a preferable approach to increase trust in the cloud. In this paper, after briefly discussing our test-based certification scheme for the cloud, we show a real certification process aimed to certify Open Stack, an open source IaaS solution for managing infrastructure resources. In particular, we first describe the testing activities executed to certify Open Stack for security and performance properties. We then illustrate the obtained results and the outcomes of the certification process.

The aim of this work was to develop a lumped parameter model of the cardiovascular system and to couple it with a model of respiratory mechanics. In comparison to existing models, modifications and additions have been implemented to include a model of the upper limb vasculature employing the electrical analogy of hemodynamic variables. The model prediction of respiratory effects on arterial pressure was compared with in vivo invasive measurement of blood pressure in patients. The model indicates that the inherent coupling between the cardiovascular and respiratory systems can be described by mathematical relationships of physiological parameters with robust predictions. With specification of parameters based on individual measurements of cardio-respiratory variables, the model can be used in the clinical setting of intensive care units to predict hemodynamic changes and to optimize ventilation and volume loading strategies.

Although the commercial exploitation of Ka-band is finally taking place with an important delay as compared to the initial market forecasts, it is clear that there is a need to start developments in new frequency bands for supporting the future deployment of satellite broadband services able to satisfy the growing need for broadcast interactive applications. In fact, the demand for increasing data rates and offered capacity, combined with the need of wider bandwidths, is forcing the newly conceived satellite systems toward progressively higher frequencies. In this perspective, the wide bandwidth allocated by the International Telecommunication Union (ITU) to satellite services in Q/V, makes these frequencies the most promising candidates for the emerging broadband systems.

In order to support the deployment of satellite broadband services able to satisfy the growing need for broadcast interactive applications, future broadband telecommunication satellites will have to exploit frequencies beyond Ka-band. This entails new key challenges and the use of critical techniques and technologies, which will be discussed.

The paper carries out a preliminary assessment of how mobile satellite broadcasting (MSB) systems can increase their capacity potential with a high degree of flexibility and, at the same time, remain on par with wireless terrestrial counterparts. As argued in this work, a promising way forward in this regard is the migration from the conventional single polarization per beam to an advanced dual polarization per beam architecture, also benefitting from recent advancement in multibeam antenna techniques. This work summarizes results of recent studies on dual polarization MSB from a system, interference, antenna, channel, capacity, and FEC uncoded MIMO performance perspective, highlighting along the course the major milestones and challenges.

In this paper we review key properties of recently proposed high performance protocols for Random Access (RA) satellite channels for both Time Division and Code Division Multiple Access (TDMA/CDMA) techniques. The proposed protocols by far outperform traditional satellite random access techniques without the need for quick feedback from the gateway. This makes possible to avoid the utilization of demand assigned capacity for the transmission of small/medium size bursts of packets. A fair comparative performance of state-of-the-art TDMA and CDMA RA schemes is provided together with a summary of their key performance results. It is shown that the proposed enhanced RA protocols, although different between TDMA and CDMA, share commonalities as they exploit iterative interference cancellation at the demodulator side and demonstrate to provide even better performance in the presence of received carrier power unbalance. Typical application scenarios of these enhanced random access protocols are then illustrated, as well as possible ways to combine random access and demand assigned protocols.

The manuscript describes the design drivers and performance of a high efficiency quasi-real time satellite mobile messaging system well adapted to the location-based and data acquisition services targeting in particular the automotive market. It is shown that the proposed solution is providing a random access channel throughput around 2 bit/s/Hz with reliable packet delivery over satellite mobile channels. This very high throughput is obtained by a relatively simple packet transmission control based on downlink signal quality observation and an optimized design of spread Aloha with successive interference cancelation (SIC) at the gateway.

Herein, the results of the ESA co-funded research project named "ORTIGIA" are summarized The scope of the project was to validate experimentally the techniques introduced by the DVB-SH working group to counteract fading in satellite and terrestrial environments. The experiments include measurements both on the field and in the laboratory.

Prior to the design and development phase of the European Galileo programme, the European Space Agency (ESA) undertook several pre-development projects to reduce the overall programme risk. Navigation signal bandwidth was determined to be one key risk area. This paper describes the development and use of a highly flexible signal validation facility designed to generate and receive novel, band-limited GNSS signals. The GNSS signal validation facility consists of a fully functioned real-time GNSS constellation simulator and signal generator; a dedicated receiver, a navigation processing unit and a performance analysis software suite. The constellation simulator, receiver and navigation processing unit are capable of operating in real-time with 12 satellites in view and three frequencies per satellite. The GNSS signal validation facility itself is extremely flexible to allow performance comparisons of different satellite constellations, signal designs, code lengths, data rates and frequencies. The GNSS signal validation facility has been used in an extensive test campaign to evaluate the performance of the novel band-limited GNSS signals under realistic user conditions with a representative Galileo satellite constellation. A strong focus of the signal validation test campaign was the performance of three-carrier differential navigation algorithms. This paper briefly describes the operation of the GNSS signal validation facility and provides an overview of the main test campaign performance results. This paper contains the first published results from the GNSS signal validation facility. A major result from the test campaign is that the novel band-limited GNSS signals provide robust and accurate positioning capability with navigation data rates of up to 3000 s/s. The receiver was shown to receive 24 MHz band-limited signals with a loss of less than 1 dB for a spreading code of 15.345 Mc/s and a sampling frequency of 56 MHz.

The European Telecommunication Standards Institute (ETSI) decision to endorse for the Universal Telecommunication Radio Access (UTRA) techniques based upon wideband CDMA approaches for terrestrial UMTS (T-UMTS) paired frequency duplexing band will certainly constitute an important driver to steer the corresponding choice for the satellite UMTS (S-UMTS) component. In this paper it is shown how a similarity in the S-UMTS access solution not only contributes to making dual-mode user-terminals more cost-effective but also represents a good technical choice. This is despite the fact that the satellite UMTS component faces a number of unique challenging requirements, such as very scarce RF power resources compared to T-UMTS, significant propagation delay, high frequency variations due to Doppler shift (especially for the low-altitude Earth orbit (LEO) case), larger cell size. This paper described the main ETSI UTRA modifications required to obtain an efficient S-UMTS air interface capable of suiting the above listed constraints, while keeping maximum commonality with the T-UMTS.

The performance of the European Space Agency (ESA) spacecraft telecommand subsystem due to simultaneous ranging is analyzed. The use of the ESA multipurpose tracking system, which represents an improved version of the deep space tracking system, is assumed. Numerical results show that the telecommand bit error rate degradation is negligible and that the frequency optimization proposed by T.M. Nguyen (IEEE 1987 National Symp. on Electromag. Compat., Conf. Record, p.308-17) is not applicable because of the wrong Fourier code expansion proposed. It is also shown that the interference level strongly depends on the relative phase between the telecommand subcarrier and the ranging tone, so that it cannot be neglected as assumed by Nguyen. >

The authors propose an innovative code division multiple access (CDMA)-based mobile system for voice (and data) services. The system makes use of voice activation in order to increase the CDMA efficiency (useful transmitted information vs. occupied bandwidth). The synchronization problems are solved by distributing a master code in the forward link and using forced link activation in the return when no speech activity is detected. The blocking probability is minimized by means of multirate speech coding associated with a centralized network control. Bit error rate calculations show all the advantages of operating in a synchronous mode. >

A theoretical analysis (confirmed and integrated by computer simulations) of the effect of coherent interference on a pseudo-noise/spread-spectrum (PN/SS) signal in satellite communications systems when a hard-limited transponder is used is presented. A general formula is derived which allows one to determine the signal-to-interference-power ratio degradation in the transponder, in the case of either continuous-wave or modulated interference, and in the presence of additive white Gaussian noise at the transponder input. Special attention is devoted to the phenomenon of complete annihilation of the spread-spectrum signal occurring for particular coherence relationships between signal and interferer. Interference characteristics of most commonly employed modulation schemes such as QPSK and MSK are explicitly reported. >

Trellis-coded quasi-orthogonal code-division multiplexing (TCQO-CDM) is introduced as a transmission technique for digital audio broadcasting. The technique shows good performance over the satellite L-band fading channel and also in the terrestrial gap-filler type of transmission. Preliminary satellite link budgets based on extensive computer simulation results are provided. The capacity achievable by the terrestrial single-frequency gap-filler network utilizing the same satellite frequency and user receiver is also discussed. Numerical results show that remarkable capacity can be achieved utilizing high-Earth-orbit satellites complemented by terrestrial gap-filler transmission. A variety of transmission rates and hence broadcasting services can be realized. It is shown that a geostationary satellite can provide limited service availability and limited capacity to mobile users but can be used for experimental purposes. >

Synchronous trellis-coded code division multiple access (S-TC-CDMA) is introduced and analyzed. Compared with uncoded synchronous CDMA and conventional CDMA systems, S-TC-CDMA greatly improves the power and/or bandwidth efficiency using trellis coded M-ary phase shift keying (PSK) or quadrature amplitude modulation (QAM) modulation in conjunction with independent quasi-orthogonal I-Q direct sequence spectrum spreading (DS/SS). Approximate system bit error rate performances derived for an additive white Gaussian noise (AWGN) channel with cochannel interference are favorably compared to computer simulation results. Impairments due to satellite nonlinearities and multipath channel fading are discussed, and system peformance is reported. >

The European Space Agency (ESA) is studying different transmission techniques suited for satellite sound broadcasting services. The authors report preliminary results about the performance of two efficient transmission techniques, namely coded orthogonal frequency division multiplexing and coded quasi-orthogonal code division multiplexing. By means of a computer simulation approach, the performance of the two systems has been evaluated over the nonlinear satellite fading channel. Link budgets have been established for the case of highly elliptical orbit (HEO) and geostationary orbit (GEO) satellites. Results show that both approaches are suited for satellite radio broadcasting presenting similar impairments over the nonlinear satellite fading channel. >

Trellis-coded 8-PSK (TC-8-PSK) modulation is a power and bandwidth efficient modulation scheme which is finding increasing applications in terrestrial and satellite systems. In particular, TC-8-PSK is demonstrating attractive performances over the satellite mobile fading channel where it provides considerable coding gain with respect to uncoded QPSK with no bandwidth efficiency loss. In the paper the capabilities of a decision-directed maximum-likelihood coherent phase tracker are investigated for the flat Rician fading channel. By optimizing the phase loop parameters in the presence of Rician fading with respect to the mean time to lose lock, it is shown that, for typical satellite fading channels, the coherent decision-directed phase tracker performs poorly. This is also true for the feedforward decision-feedback phase estimator. In these cases, the additional power loss required by differential detection of TC-8-PSK with respect to coherent detection has been evaluated by means of computer simulations. >

Sixteen-level quadrature amplitude modulation (16-QAM) is considered a power-inefficient transmission technique for satellite communication systems. The authors present design criteria of an all-digital demodulator for rate-3/4 TC 16-QAM which attains a BER of 10/sup -5/ with a power savings of roughly 3.5 dB in a typical nonlinear channel, when compared to conventional uncoded 8-PSK. This figure includes all of the impairments produced by increased satellite amplifier output back off (OBO) and by the presence of the subsystems for symbol timing recovery, carrier phase estimation and automatic gain control. A key factor in achieving such a good performance is the compensation of the nonlinear distortion of the received signal constellation by means of a modified metrics computation in the Viterbi decoder. With the aid of this particular technique, it is possible to move the optimum operating point of the amplifier much closer to saturation than in the conventional case, without any need for on-board amplifier linearization. >

We take into consideration a low-complexity blind adaptive interference-rejection detector (BAID) scheme that minimizes the detrimental effect of the multiple access interference (MAI) on the bit-error rate (BER) performance of the data demodulator for direct-sequence/spread-spectrum (DS/SS) signals in CDMA radio networks. Specifically, we describe a few modifications to the original algorithm that make it more suitable to a practical implementation with QPSK-modulated DS/SS signals and asynchronous multiplexing, and we evaluate the performance of such extended detector in the case of coherent signal detection.

The dramatic performance improvements lately experienced by application-specific integrated circuits (ASICs) let us envisage a single-chip all-digital implementation of a data modem for direct-sequence spread spectrum (DS/SS) code-division multiple access (CDMA) systems. In this respect, it is of interest to represent the signals in the digital domain with a small number of bits. On the other hand, it is known that coarse signal quantization may cause a significant bit error rate (BER) performance degradation. This paper investigates on the impact of signal quantization on the BER performance of a DS/SS CDMA receiver in the presence of Gaussian noise and cochannel interference. Based on a general theoretical analysis, a few multiple access strategies are taken into consideration, and some simple design hints are derived and verified by computer simulation.

Code division multiple access (CDMA) techniques have received a great deal of attention for mobile terrestrial/satellite communication systems. Primarily considered for the noteworthy features of low power flux density emission and robustness to interference and multipath, CDMA is known to provide reduced bandwidth and power efficiency when compared to traditional TDMA and FDMA due to the intrinsic co-channel self-noise. Practical solutions, under advanced development status in Europe and in the USA, respectively, propose to overcome such a shortcoming by implementing orthogonal CDMA signalling in the outbound link. The paper is focused on the comparative performance analysis of those two orthogonal CDMA schemes in the operating conditions of a mobile satellite communications system. In particular, starting from the analysis of the classical additive white Gaussian noise (AWGN) environment, the two CDMA systems are compared in the presence of carrier phase offset, frequency-selective multipath fading, and a typical satellite transponder nonlinearity.

An all-digital 8PSK (phase shift keying) demodulator including decision-directed carrier phase and clock timing recovery is introduced and analyzed. The proposed synchronization algorithms require two samples per symbol. The phase and timing discriminator characteristics are analytically derived and checked by means of computer simulations. Simulated steady-state carrier phase and clock timing mean square error results are compared with analytical findings and the Cramer-Rao bound. Mean acquisition time for joint phase and timing error has also been computed by the Monte Carlo simulation technique. Finally, digital demodulator performance in terms of bit error rate for uncoded and trellis coded 8PSK, including interpolators and synchronization loops, is presented. >

A noncoherent digital delay lock loop (D-DLL) suited for code tracking in direct-sequence/spread-spectrum (DS/SS) band-limited (BL) signals is presented and analyzed. The key feature of this tracking scheme is the requirement of only one example per chip to derive the loop error signal. The expression of the S-curve of the proposed scheme is derived theoretically and checked by a time-domain computer simulation. Moreover, the steady-state RMS chip timing jitter of the D-DLL is derived, and results are compared with computer simulations. The proposed synchronization scheme is shown to bear smaller chip timing jitter when compared to the analog scheme for rectangular shaped chips. >