| |
 | |
| |
| Authors: Scotti, F.; Zhang, D.; ; Abstract: The six papers in this special issue present a useful insight into some of the most prominent techniques and applications in the biometric instrumentation and measurement field. |
| Authors: Wang, D.; Zhang, Y.; Yao, C.; Wu, J.; Jiao, H.; Liu, M.; ; Abstract: A compact pen-type force sensor is developed to study the feasibility of force-based signature verification. A force-sensing method based on leverage effect is proposed to detect 3-D forces between the pen's tip and the paper. A compact and low-cost force-sensing assembly is designed, which is integrated by five off-the-shelf 1-D force sensors. A matrix-based measurement model is established to compute the force signal in the task coordinate system (CS), which is transformed from the force signal in the Sensor CS and the angle signal from a 2-D angle sensor. The structural parameters of the force sensor are determined both to achieve the required force accuracy and to meet the constraints of pen size for comfortable grasping. System performance experiments are carried out to measure the absolute and repetitive accuracy of the pen. The results show that the pen is capable for detection of 3-D force signals during real-time handwriting. Repetitive accuracy is measured to be about 0.05 N. Finally, a small-scale signature verification experiment is carried out. The verification results based on the dynamic time warping (DTW) method show that the equal error rate (EER) is about 6.3%, which illustrates the potential of the pen for force-based signature verification. |
| Authors: Tao, Q.; Veldhuis, R.; ; Abstract: We propose a secure, robust, and low-cost biometric authentication system on the mobile personal device for the personal network. The system consists of the following five key modules: 1) face detection; 2) face registration; 3) illumination normalization; 4) face verification; and 5) information fusion. For the complicated face authentication task on the devices with limited resources, the emphasis is largely on the reliability and applicability of the system. Both theoretical and practical considerations are taken. The final system is able to achieve an equal error rate of 2% under challenging testing protocols. The low hardware and software cost makes the system well adaptable to a large range of security applications. |
| Authors: McKeon, R. T.; Flynn, P. J.; ; Abstract: Many commercially available 3-D sensors suitable for face image capture employ passive or texture-assisted stereo imaging or structured illumination with a moving light stripe. These techniques require a stationary subject. We describe an initial design and evaluation of a fixed-stripe moving object 3-D scanner designed for human faces. Our method of acquisition requires the subject to walk through a static light screen generated by two laser line projectors. Triangulation and tracking applied to the video sequences captured during subject motion yield a 3-D image of the subject's face from multiple images. To demonstrate the accuracy of our initial design, a small-scale facial recognition experiment was executed. In an experiment involving 81 subjects with four images per subject on the average, we used two gallery images per subject, and we achieved 89.6% rank-one recognition using an iterative closest point (ICP)-based matching method, demonstrating the feasibility of the technique. |
| Authors: Kukula, E. P.; Sutton, M. J.; Elliott, S. J.; ; Abstract: This paper discusses the human–biometric-sensor interaction (HBSI) evaluation method that uses ergonomics, usability, and sample quality criteria as explanatory variables for the overall biometric system performance. The HBSI method was proposed because of questions regarding the thoroughness of traditional system-level performance evaluation metrics such as the failure-to-acquire (FTA) rate, the failure-to-enroll (FTE) rate, the false-accept rate (FAR), and the false-reject rate (FRR). Data were collected from 85 individuals over three visits that accounted for 25 867 user interactions with three swipe-based fingerprint sensors. The results in this paper revealed that traditional biometric evaluations that focus on system-level metrics are not providing sufficient reporting details regarding the user interaction with the devices. In this paper, the systemic FTA rate of 14.38% was shown to be segmented into three metrics: false interaction (FI), failure to detect (FTD), and concealed interaction (CI). The results show that the FI accounted for 69.05% of the systemic FTA presentations, FTD accounted for 30.71%, and CI accounted for 0.24%. Overall, the HBSI evaluation method and framework for biometric interactions provided new metrics that improve the analysis capabilities for biometric performance evaluations as it links system feedback to the human–sensor interaction, enabling researchers, system designers, and implementers to understand if the issues are the result of the system, the user, both the system and the user, or some other extraneous factor. |
| Authors: Hosseini, M. S.; Araabi, B. N.; Soltanian-Zadeh, H.; ; Abstract: Recognition of iris based on visible light (VL) imaging is a difficult problem because of the light reflection from the cornea. Nonetheless, pigment melanin provides a rich feature source in VL, which is unavailable in near-infrared (NIR) imaging. This is due to the biological spectroscopy of eumelanin, a chemical not stimulated in NIR. In this case, a plausible solution to observe such patterns may be provided by an adaptive procedure using a variational technique on the image histogram. To describe the patterns, a shape analysis method is used to derive the feature code for each subject. An important question is how the melanin patterns, which are extracted from VL, are independent of the iris texture in NIR. With this question in mind, the present investigation proposes fusion of features extracted from NIR and VL to boost recognition performance. We have collected our own database (UTIRIS), consisting of both NIR and VL images of 158 eyes of 79 individuals. This investigation demonstrates that the proposed algorithm is highly sensitive to the patterns of chromophores and improves the iris recognition rate. |
| Authors: Sellahewa, H.; Jassim, S. A.; ; Abstract: The accuracy of automated face recognition systems is greatly affected by intraclass variations between enrollment and identification stages. In particular, changes in lighting conditions is a major contributor to these variations. Common approaches to address the effects of varying lighting conditions include preprocessing face images to normalize intraclass variations and the use of illumination invariant face descriptors. Histogram equalization is a widely used technique in face recognition to normalize variations in illumination. However, normalizing well-lit face images could lead to a decrease in recognition accuracy. The multiresolution property of wavelet transforms is used in face recognition to extract facial feature descriptors at different scales and frequencies. The high-frequency wavelet subbands have shown to provide illumination-invariant face descriptors. However, the approximation wavelet subbands have shown to be a better feature representation for well-lit face images. Fusion of match scores from low- and high-frequency-based face representations have shown to improve recognition accuracy under varying lighting conditions. However, the selection of fusion parameters for different lighting conditions remains unsolved. Motivated by these observations, this paper presents adaptive approaches to face recognition to overcome the adverse effects of varying lighting conditions. Image quality, which is measured in terms of luminance distortion in comparison to a known reference image, will be used as the base for adapting the application of global and region illumination normalization procedures. Image quality is also used to adaptively select fusion parameters for wavelet-based multistream face recognition. |
| Authors: Mair, R. G.; ; Abstract: Near-field communication (NFC) devices, which is derived from radio frequency identification systems, provide a robust and simple wireless data interface. To make their use even more convenient, they shall always stay activated and scan the environment for passive communication partners. Usually, this is accomplished by protocol command inquiries. Since this interface is built into handheld battery-powered devices, power consumption is a major concern. Therefore, a low-power scan method is needed to ensure long battery life. We propose a solution that can easily be realized on silicon, can achieve a polling rate that ensures nearly no noticeable delay when establishing a connection, and consumes only 1% of the energy per interrogation when compared to the traditional approach. These tremendous savings in power make NFC viable for ad hoc networking. |
| Authors: Bondavalli, A.; Ceccarelli, A.; Falai, L.; Vadursi, M.; ; Abstract: In recent years, experts in the field of dependability are recognizing experimental measurements as an attractive option for assessing distributed systems; contrary to simulation, measurement allows monitoring the real execution of a system in its real usage environment. However, the results of a recent survey have highlighted that the way measurements are carried out and measurement results are expressed is far from being in line with the approach commonly adopted by metrology. The scope of this paper is twofold. The first goal is to extend the discussion on the increasing role that measurements play in dependability and on the importance of cross-fertilization between the dependability and the instrumentation and measurement communities. The second objective is to present a different approach to dependability measurements, in line with the common practices in metrology. With regard to this, the paper presents a tool for dependability measurements in distributed systems that allows evaluating the uncertainty of measurement results. The tool is an enhancement of NekoStat, which is a powerful highly portable Java framework that allows analyzing distributed systems and algorithms. Together with the description of the tool and its innovative features, two experimental case studies are presented. |
| Authors: Kuperman, A.; Tapuchi, S.; Makarenko, S.; Suissa, U.; ; Abstract: A new method for capacitance increase is proposed, thus allowing for capacitance standards with a sixfold higher value than those currently found in the market. The method can be used for capacitance increase in any standard and provides a solution for calibration problems of high-capacitance four-terminal meters. The increase in capacitance is based on the introduction of inductive coupling between the current and potential circuits in devices with four electrodes. The output capacitance is created by the summation of the capacitive and inductive parameters that were formed in various channels. The operating frequency range resides at the left of the resonant frequency and is separated from the resonance by a range of frequencies called “protective band.” The limitations on the width of this band and the quality factor are considered in this paper and are discussed in depth. It is shown that standards should be calibrated on each operating frequency when using the proposed method. The uncertainties of the method are also analyzed, and the factors that affect the uncertainty increase are clearly indicated. Simulation and experimental results are presented to verify the proposed method and demonstrate its feasibility. |
| Authors: Fernandes, C. W.; Bellar, M. D.; Werneck, M. M.; ; Abstract: In this paper, an optical flowmeter based on the cross-correlation technique is proposed. Two parallel laser beams are made to cross a transparent pipe wherein a turbulent air flows. The laser beams are detected by two position-sensitive detectors (PSDs) whose output signals are processed by software. The cross-correlation function between the signals is calculated, which yields the time delay between them. The flow velocity is then obtained by the ratio of the distance between the laser beams to the time delay. The flowmeter is applicable for measuring human respiratory flow in a noninvasive way. An experimental prototype is built, and results are provided. A detailed description of the experimental setup and of measurement procedures are presented and discussed. Results have been very promising and have shown the potential of the system developed here in performing human respiratory flow measurements, particularly those suitable for neonates. |
| Authors: Hsu, J.; Su, C.; ; Abstract: This paper presents a built-in jitter measurement approach for measuring the timing jitter of spread-spectrum clocks (SSCs) and a jitter estimation method for validating the approach. Because of the lack of dedicated measurement instruments for SSC timing jitter measurement, the jitter estimation method is proposed to correlate SSC and non-SSC jitter. A 1.2-GHz eight-phase SSC generator with the jitter measurement circuit is designed and fabricated using the 0.18-$muhbox{m}$ complementary metal–oxide–semiconductor technology. The measured results are validated by the proposed estimation method, which is the key contribution of this paper. The experimental results show that the proposed built-in measurement approach has an error of less than 0.0026 UI. |
| Authors: Penella, M. T.; Gasulla, M.; ; Abstract: The sensor nodes of wireless sensor networks remain inactive most of the time to achieve longer runtimes. Power is mainly provided by batteries, which are either primary or secondary. Because of its internal impedance, a significant voltage drop can appear across the battery terminals at the activation time of the node, thus preventing the extraction of all the energy from the battery. Additionally, internal losses can also be significant. Consequently, the runtime is reduced. The addition of a supercapacitor in parallel with the battery, thus forming a hybrid-storage device, has been proposed under pulsed loads to increase the power capabilities and reduce both the voltage drop and the internal losses at the battery. However, this strategy has not yet thoroughly been analyzed and tested in low-power wireless sensor nodes. This paper presents a comprehensive theoretical analysis that extends previous works found in the literature and provides design guidelines for choosing the appropriate supercapacitor. The analysis is supported by extensive experimental results. Two low-capacity ( $< 200 hbox{mAh}$) batteries were tested together with their hybrid-storage unit counterparts when using an electronic load as a pulsed current sink. The hybrid-storage units always achieved a higher runtime. One of the batteries was also tested using a sensor node. The runtime extension was 16% and 33% when connecting the hybrid-storage unit directly and through a dc–dc switching regulator to the sensor node, respectively. |
| Authors: Piskorowski, J.; ; Abstract: In many measurement applications, it is required to have notch filters that simultaneously possess a very selective magnitude response (high quality factor $Q$) and a transient response of short duration. However, increasing the quality factor also increases the duration of the transient process in the filter after the action of the excitation. This paper presents a new concept of digital IIR notch filters, whose quality factor changes with time. Owing to a temporary change in the value of the quality factor, the transient can considerably be reduced. Simulations verifying the effectiveness of the proposed $Q$-varying IIR notch filter are presented and compared with the performance of the traditional $Q$-constant filter using ECG signals with unwanted sinusoidal interference as a study case. |
| Authors: Kolmonen, V.-M.; Almers, P.; Salmi, J.; Koivunen, J.; Haneda, K.; Richter, A.; Tufvesson, F.; Molisch, A. F.; Vainikainen, P.; ; Abstract: In this paper, we present and evaluate the performance of a dynamic dual-link wideband multiple-input–multiple-output (MIMO) channel sounder. The channel sounder can simultaneously measure two wideband dual-polarized links, each with a MIMO matrix size of 30 $times$ 30 and 30 $times$ 32. Multilink MIMO systems, including multiuser and cooperative MIMO, are essential parts of future high-throughput wireless local area networks and fourth-generation cellular systems. To fully understand such systems, the dynamic characteristics of multilink MIMO channels have to be measured. In this paper, we present a channel sounder that enables such measurements, including double-directional parameter estimation possibility for both links. The presented dual-link MIMO channel sounder does not suffer from the deficiencies of previous “virtual multiuser”measurement systems. Furthermore, system analysis and sample results from a measurement campaign with this channel sounder at 5.3 GHz in an indoor office environment are presented. |
| Authors: Yang, B.; Li, S.; ; Abstract: To obtain an image with every object in focus, we always need to fuse images taken from the same view point with different focal settings. Multiresolution transforms, such as pyramid decomposition and wavelet, are usually used to solve this problem. In this paper, a sparse representation-based multifocus image fusion method is proposed. In the method, first, the source image is represented with sparse coefficients using an overcomplete dictionary. Second, the coefficients are combined with the choose-max fusion rule. Finally, the fused image is reconstructed from the combined sparse coefficients and the dictionary. Furthermore, the proposed fusion scheme can simultaneously resolve the image restoration and fusion problem by changing the approximate criterion in the sparse representation algorithm. The proposed method is compared with spatial gradient (SG)-, morphological wavelet transform (MWT)-, discrete wavelet transform (DWT)-, stationary wavelet transform (SWT)-, curvelet transform (CVT)-, and nonsubsampling contourlet transform (NSCT)-based methods on several pairs of multifocus images. The experimental results demonstrate that the proposed approach performs better in both subjective and objective qualities. |
| Authors: Brunetto, P.; Fortuna, L.; Giannone, P.; Graziani, S.; Strazzeri, S.; ; Abstract: Several models that describe the behavior of ionic polymer–metal composite (IPMC)-based actuators can be found in the literature. The response of IPMC transducers as a function of modifying quantities is a matter of interest; however, it has not been investigated. It is reasonable to argue that environmental humidity and temperature represent the main modifying parameters. In fact, humidity changes the behavior of IPMC transducers, working as both sensors and actuators, because it changes the Young modulus of the devices and, hence, their mechanical response. The influence of temperature is suspected, because polymer characteristics are often influenced by this quantity. In a previous paper, the authors proposed a dynamic model and investigated the scaling effect of geometrical parameters, giving evidence of the excellent agreement between estimations that were obtained using the proposed model and corresponding observations. In this paper, the response of IPMC actuators to both temperature and relative humidity is analyzed, giving interesting information that both integrates IPMC models and allows for a better exploitation of IPMCs. |
| Authors: Fang, J.; Gong, X.; ; Abstract: This paper deals with the problem of state estimation for the integration of an inertial navigation system (INS) and Global Positioning System (GPS). For a nonlinear system that has the model error and white Gaussian noise, a predictive filter (PF) is used to estimate the model error, and based on this, a modified iterated extended Kalman filter (IEKF) is proposed and is called predictive iterated Kalman filter (PIKF). The basic idea of the PIKF is to compensate the state estimate by the estimated model error. An INS/GPS integration system is implemented using the PIKF and applied to synthetic aperture radar (SAR) motion compensation. Through flight tests, it is shown that the PIKF has an obvious accuracy advantage over the IEKF and unscented Kalman filter (UKF) in velocity. |
| Authors: Jargon, J. A.; Hale, P. D.; Wang, C. M.; ; Abstract: In this paper, we describe an apparatus for correcting the timebase errors when calibrating the response of an equivalent-time sampling oscilloscope using a passively mode-locked erbium-doped fiber laser that is phase locked to a microwave signal generator. This enables us to simultaneously correct both the random jitter and the systematic timebase distortion in the oscilloscope. As a demonstration of the technique, we measure the electrical pulse generated by a fast photodiode that is excited by our laser. We show that the pulse that is reconstructed using our technique has significantly lower uncertainty than the pulse that is reconstructed using a separate correction for timebase distortion followed by jitter deconvolution. |
| Authors: Ding, Y.; Dai, X.; Zhang, T.; ; Abstract: To precisely measure temperature in high-voltage electrical power equipment subject to intense electromagnetic interference (EMI), we present an artificial neural network (ANN) inverse compensating method, based on which we also construct a compounded fiber-optic temperature measurement system (CFOTMS). The CFOTMS consists of a fiber-optic semiconductor absorption temperature sensor (FOSATS) and an ANN inverse compensator. On one hand, optical-fiber-based light transmission is insusceptible to EMI; on the other hand, due to the utilization of the ANN inverse compensator, the dynamic performance and measuring precision of the CFOTMS are significantly enhanced compared with the sole use of the sensor. Therefore, it is very suitable to be used in high-voltage electrical power equipment. Furthermore, as the intensity-dependent FOSATS is a cheap device, and the ANN inverse compensator is realized in software, the cost of the CFOTMS will be low, which makes it suitable to be used in economical equipment. |
| Authors: Gao, H.; Xu, W.; Sun, J.; Tang, Y.; ; Abstract: Multilevel thresholding is one of the most popular image segmentation techniques. Some of these are time-consuming algorithms. In this paper, by preserving the fast convergence rate of particle swarm optimization (PSO), the quantum-behaved PSO employing the cooperative method (CQPSO) is proposed to save computation time and to conquer the curse of dimensionality. Maximization of the measure of separability on the basis of between-classes variance method (often called the OTSU method), which is a popular thresholding technique, is employed to evaluate the performance of the proposed method. The experimental results show that, compared with the existing population-based thresholding methods, the proposed PSO algorithm gets more effective and efficient results. It also shortens the computation time of the traditional OTSU method. Therefore, it can be applied in complex image processing such as automatic target recognition. |
| Authors: Mishra, S. K.; Panda, G.; Das, D. P.; ; Abstract: This paper proposes a simple and novel method of designing and developing high-linearity linear variable differential transformer (LVDT)-based displacement sensing systems. Conventionally, precise adjustment of windings is made to enhance the linearity range of LVDTs. The tedious job of pitch adjustment of windings of LVDTs can be overcome by using the proposed method. A functional link artificial neural network has been successfully used in this paper for nonlinear compensation of the LVDT. The effectiveness of the proposed method is demonstrated through computer simulation with the experimental data of two different LVDT. The complete algorithm with the practical setup for the development of a linear LVDT is presented in this paper. |
| Authors: Kusljevic, M. D.; ; Abstract: A number of measurement algorithms apply orthogonal signal components obtained by two orthogonal finite-impulse-response (FIR) filters. The most significant error in orthogonal FIR digital-filter-based measurement algorithms arises due to the FIR filters having different magnitude gains at frequencies other than the nominal power system frequency. In addition, although the FIR filters show complete rejection of harmonics when the power system frequency is equal to the nominal, this is not the case for other values of the power system frequency. To alleviate this drawback, the filter parameters have to be adapted during frequency estimation. Suitable implementations of adaptive filters that allow closed-form calculation of coefficients, such as cascade FIR comb filters and resonator-based filters, are present in the literature. In this paper, the advantages and pitfalls of these two techniques are addressed with regard to computational complexity, coefficient sensitivity problems, and convergence. As a result, an improved and very suitable combined algorithm based on parallel resonators with common feedback combined with an external FIR comb-filter-based module for frequency estimation that is applied on antialiasing-filtered and decimated input signal is proposed. The obtained simulation results allow us to establish the performance of the proposed algorithm by comparing its measurement precision with the results obtained using fast Fourier transform (FFT) implementations. It has been found that the proposed algorithm is suitable for real-time applications. |
| Authors: Wegmueller, M. S.; Oberle, M.; Felber, N.; Kuster, N.; Fichtner, W.; ; Abstract: Galvanic coupling is a promising approach for wireless intrabody data transmission between sensors. Using the human body as a transmission medium for electrical signals becomes a novel data communication technique in biomedical monitoring systems. In this paper, special attention is given to the coupling of the current into the human body. Safety requirements have to be fulfilled, and optimal signal coupling is of essence. Therefore, different electrodes are compared. A test system offers up to 1 mA contact current modulated in the frequency range of 10 kHz to 1 MHz. The injected current is up to 20 times below the maximum allowed contact current. Such a low-current approach enables data communication that is more energy saving than other wireless technologies. |
| Authors: Reungpeerakul, T.; Kay, D.; Mourad, S.; ; Abstract: A mixed-mode built-in self-test (BIST) approach that deploys two new techniques is presented in this paper. Partial pattern matching allows the reduction of the number of patterns used for detecting random-pattern-resistant faults without relying on fault simulation. A multiple-control sequence is used to guide the linear feedback shift register (LFSR) to generate these patterns at application time. The advantages of this method include the reduction of the test data volume, the shortening of the test application time, and its reusability for logic cores on a system-on-chip (SOC). |
| Authors: Falk, T. H.; Chan, W.-Y.; ; Abstract: In this paper, short- and long-term temporal dynamic information is investigated for the blind measurement of room acoustical parameters. In particular, estimators of room reverberation time $(T_{60})$ and direct-to-reverberant energy ratio (DRR) are proposed. Short-term temporal dynamic information is obtained from differential (delta) cepstral coefficients. The statistics computed from the zeroth-order delta cepstral sequence serve as input features to a support vector $T_{60}$ estimator. Long-term temporal dynamic cues, on the other hand, are obtained from an auditory spectrotemporal representation of speech commonly referred to as modulation spectrum. A measure termed as reverberation-to-speech modulation energy ratio, which is computed per modulation frequency band, is proposed and serves as input to $T_{60}$ and DRR estimators. Experiments show that the proposed estimators outperform a baseline system in scenarios involving reverberant speech with and without the presence of acoustic background noise. Experiments also suggest that estimators of subjective perception of spectral coloration, reverberant tail effect, and overall speech quality can be obtained with an adaptive speech-to-reverberation modulation energy ratio measure. |
| |
| |
| |
| |
