Interval-censored failure time data occur in many medical investigations as well as other studies such as demographical and sociological studies. They include the usual right-censored failure time data as a special ca...
详细信息
Interval-censored failure time data occur in many medical investigations as well as other studies such as demographical and sociological studies. They include the usual right-censored failure time data as a special case but provide much more complex structure and less relevant information than the right-censored data. This article reviews some basic concepts, issues and the corresponding statistical approaches related to the analysis of interval-censored data as well as recent advances. In particular, we discuss estimation of a survival function, comparison of several treatments and regression analysis as well as competing risks analysis and truncation in the presence of interval censoring. A well-known example of interval-censored data is described and analysed to illustrate some of the statistical procedures discussed..
In this paper, we present a joint blind channel estimation and symbol detection for decoding a blurred and noisy 1D barcode captured image. From an information transmission point of view, we show that the channel impu...
详细信息
ISBN:
(纸本)9781424456383
In this paper, we present a joint blind channel estimation and symbol detection for decoding a blurred and noisy 1D barcode captured image. From an information transmission point of view, we show that the channel impulse response, the noise power and the symbols can be efficiently estimated by taking into account the signal structure such as the cyclostationary property of the hidden Markov process to estimate. Based on the expectation-maximisation method, we show that the new algorithm offers significative performance gain compared to classical ones pushing back the frontiers of the barcode technology.
In this paper, we estimate the time-of-arrival (ToA) of wireless channels by using the widely adopted equally-spaced channel estimator for the multi-band orthogonal frequency-division multiplexing (MB-OFDM) ultrawide-...
详细信息
ISBN:
(纸本)9781424481804
In this paper, we estimate the time-of-arrival (ToA) of wireless channels by using the widely adopted equally-spaced channel estimator for the multi-band orthogonal frequency-division multiplexing (MB-OFDM) ultrawide-band (UWB) system. By suppressing the energy leakage due to the imperfect sampling of the leading channel paths, a novel ToA estimator is proposed for the MB-OFDM UWB system. This ToA estimator is evaluated and compared with the space alternating generalized expectation maximization (SAGE) algorithm in IEEE 802.15.4a UWB channels. Simulation results show that the proposed ToA estimator performs well in all channel models and outperforms SAGE by directly locating the first channel path.
Given a set of rating data for a set of items, determining preference levels of items is a matter of importance. Various probability models have been proposed to solve this task. One such model is the Plackett-Luce mo...
详细信息
Given a set of rating data for a set of items, determining preference levels of items is a matter of importance. Various probability models have been proposed to solve this task. One such model is the Plackett-Luce model, which parameterizes the preference level of each item by a real value. In this letter, the Plackett-Luce model is generalized to cope with grouped ranking observations such as movie or restaurant ratings. Since it is difficult to maximize the likelihood of the proposed model directly, a feasible approximation is derived, and the em algorithm is adopted to find the model parameter by maximizing the approximate likelihood which is easily evaluated. The proposed model is extended to a mixture model, and two applications are proposed. To show the effectiveness of the proposed model, numerical experiments with real-world data are carried out.
Microstrip transmission line (MS), coplanar waveguide transmission line (CPW), grounded coplanar waveguide transmission line (GCPW), slow-wave transmission line with slotted grounded shields (GSCPW), slow-wave transmi...
详细信息
ISBN:
(纸本)9781424457601
Microstrip transmission line (MS), coplanar waveguide transmission line (CPW), grounded coplanar waveguide transmission line (GCPW), slow-wave transmission line with slotted grounded shields (GSCPW), slow-wave transmission line with slotted floating shields (FSCPW) are widely used in the silicon technology. Because the quasi-TEM assumption is still valid in these structures, an equivalent circuit is proposed to model all these structures. In this work, we notice that for some types of transmission lines, say GCPW and GSCPW, the per unit length capacitance increases with frequency. An LC series subcircuit is proposed to model this phenomenon. For CPW, GCPW, GSCPW and FSCPW, the model has very good accuracy and fits the measurement results very well up to the highest measurement frequency (40GHz). For MS, the results from the 3D EM simulation software are adopted and the model shows a great agreement with the simulation results up to the highest simulation frequency (100GHz).
Finding locations of the sensor nodes in Wireless Sensor Network has been an active research area in recent years. One important category of approaches uses distance measurements between anchors and sensors to localiz...
详细信息
ISBN:
(纸本)9781424456383
Finding locations of the sensor nodes in Wireless Sensor Network has been an active research area in recent years. One important category of approaches uses distance measurements between anchors and sensors to localize the unknown node. However, most approaches assume that the anchor positions are perfectly known, while in practice the anchor positions may not be accurate due to estimation errors as well as observation errors. In this paper, we study the localization of wireless sensor node with erroneous anchors, and propose an EM estimator which iteratively refines the anchor positions and estimates the sensor location. Simulation results shows that the EM estimator converges in a few iterations and outperforms the existing robust least squares algorithm.
Forecasting the condition of the equipment is becoming an important ingredient of the advanced maintenance and asset management systems. In this paper a probabilistic approach to the prognosis of damage progression in...
详细信息
ISBN:
(纸本)9781424481545
Forecasting the condition of the equipment is becoming an important ingredient of the advanced maintenance and asset management systems. In this paper a probabilistic approach to the prognosis of damage progression in gearboxes is presented. It is based on a stochastic nonlinear grey-box model of the underlying wear phenomena. Model parameters are estimated from the available vibration records by using an iterative Maximum Likelihood procedure. The procedure relies on the expectation-Maximization algorithm and the Unscented Kalman filter for estimation of hidden system states. The algorithm has been used to predict the normal operating horizon of a single-stage gearbox system. Several test runs of the system have been preformed to validate the algorithm.
In this paper, we present an iterative joint channel estimation and data detection technique for multiple-input multiple-output (MIMO) code-division multiple-access (CDMA) systems over frequency-selective fading chann...
详细信息
ISBN:
(纸本)9781424456383
In this paper, we present an iterative joint channel estimation and data detection technique for multiple-input multiple-output (MIMO) code-division multiple-access (CDMA) systems over frequency-selective fading channels. Based on the expectation-maximization (EM) algorithm, the proposed iterative receiver achieves a performance close to the optimum maximum-likelihood (ML) receiver. In addition, the performance of the proposed receiver is optimized through weight coefficients using the minimum mean-square error (MMSE) criterion. Compared to the single-user bound, our results show that the proposed receiver can mitigate the multiple-access interference and attain the full system diversity. Furthermore, our simulation results confirm that the proposed receiver is near-far resistant and offers fast convergence in severe near-far scenarios.
Time Based (TB) localization in terrestrial communications mobile radio as a complementation to global navigation satellite systems has gained recently plenty of interests. As an essential tool to develop suitable alg...
详细信息
ISBN:
(纸本)9781424456383
Time Based (TB) localization in terrestrial communications mobile radio as a complementation to global navigation satellite systems has gained recently plenty of interests. As an essential tool to develop suitable algorithms for joint communications and localizations in mobile radio networks, the wireless channel model has a growing significance. For both communications and localizations, the time evolution of multipath components is essential especially for tracking applications. Moreover, the Non Line-of-Sight (NLoS) error due to an undetectable line-of-sight path introduces an additional range error for TB localizations, which needs to be taken into account in the channel model. In this paper we present a space-alternating generalized expectation-maximization based Kalman filter method to efficiently estimate and track the time-variant multipath components based on a channel measurement campaign. The modeling of time-variant multipath characteristics, in terms of NLoS error, variance of path number, and the life span, are presented in this paper as well.
SPECT (single photon emission computerized tomography) is physically one of the worst medical imaging modalities. Despite a considerable and still increasing medical impact, its spatial resolution (beyond 1 cm) and it...
详细信息
ISBN:
(纸本)9781424441242
SPECT (single photon emission computerized tomography) is physically one of the worst medical imaging modalities. Despite a considerable and still increasing medical impact, its spatial resolution (beyond 1 cm) and its sensitivity (less than 10(-4)) are both awful. This situation is mainly due to the use of a thin parallel hole collimator. In addition the application of the unfitted radon-transform worsens the figure. We already suggested a different approach of collimation called CACAO in French standing for computer aided collimation gamma camera. This approach uses a large and long hole collimator, a different sequence of acquisition with a linear scanning motion and a dedicated reconstruction program taking full account of the depth dependent response function. Up to now, however, the CACAO project has failed to convince the scientific community of its superiority over the conventional thin hole collimator. This is due of a lack of a good reconstruction algorithm. In this paper we depict a new tomographic reconstruction algorithm for the CACAO problem. In addition to the former cited advantages, this new algorithm is exact, it takes full account of the finite geometry of the collimator holes, it reduces the type 1 statistical error (false positive) and reduces the hindering effect of points with large errors (outliers). Example of reconstruction with exact data and with a limited number of detected photons are provided. Comparison with MLEM algorithm is provided.
暂无评论