共查询到20条相似文献,搜索用时 15 毫秒
1.
The requirement of constant censoring parameter β in Koziol-Green (KG) model is too restrictive. When covariates are present, the conditional KG model (Veraverbekea and Cadarso-Suárez, 2000) which allows β to be dependent on the covariates is more realistic. In this paper, using sufficient dimension reduction methods, we provide a model-free diagnostic tool to test if β is a function of the covariates. Our method also allows us to conduct a model-free selection of the related covariates. A simulation study and a real data analysis are also included to illustrate our approach. 相似文献
2.
While existing eye detection and tracking algorithms can work reasonably well in a controlled environment, they tend to perform poorly under real world imaging conditions where the lighting produces shadows and the person’s eyes can be occluded by e.g. glasses or makeup. As a result, pixel clusters associated with the eyes tend to be grouped together with background-features. This problem occurs both for eye detection and eye tracking. Problems that especially plague eye tracking include head movement, eye blinking and light changes, all of which can cause the eyes to suddenly disappear. The usual approach in such cases is to abandon the tracking routine and re-initialize eye detection. Of course this may be a difficult process due to missed data problem. Accordingly, what is needed is an efficient method of reliably tracking a person’s eyes between successively produced video image frames, even in situations where the person’s head turns, the eyes momentarily close and/or the lighting conditions are variable. The present paper is directed to an efficient and reliable method of tracking a human eye between successively produced infrared interlaced image frames where the lighting conditions are challenging. It proposes a log likelihood-ratio function of foreground and background models in a particle filter-based eye tracking framework. It fuses key information from even, odd infrared fields (dark and bright-pupil) and their corresponding subtractive image into one single observation model. Experimental validations show good performance of the proposed eye tracker in challenging conditions that include moderate head motion and significant local and global lighting changes. The paper presents also an eye detector that relies on physiological infrared eye responses and a modified version of a cascaded classifier. 相似文献
3.
Microsystem Technologies - The aim of this work is to find an adaptive control scheme to realize precise position tracking for a piezo-actuated stage, which is usually very difficult to control due... 相似文献
4.
This work focuses on the simulation of mechanical contact between nonlinearly elastic objects, such as the components of the human body. In traditional methods, contact forces are often defined as discontinuous functions of deformations, which leads to poor convergence characteristics and high-frequency noises. We introduce a novel penalty method for finite-element simulation based on the concept of material depth, which is the distance between a particle inside an object and the objects boundary. By linearly interpolating precomputed material depths at node points, contact forces can be analytically integrated over contact surfaces without raising the computational cost. The continuity achieved by this formulation reduces oscillation and artificial acceleration, resulting in a more reliable simulation algorithm. 相似文献
5.
Parametric estimation of the dynamic errors-in-variables models is considered in this paper. In particular, a bias compensation approach is examined in a generalized framework. Sufficient conditions for uniqueness of the identified model are presented. Subsequently, a statistical accuracy analysis of the estimation algorithm is carried out. The asymptotic covariance matrix of the system parameter estimates depends on a user chosen filter and a certain weighting matrix. It is shown how these can be tuned to boost the estimation performance. The numerical simulation results suggest that the covariance matrix of the estimated parameter vector is very close to the Cramér-Rao lower bound for the estimation problem. 相似文献
6.
Output synchronization of a network of heterogeneous linear state–space models under time-varying and directed interconnection structures is investigated. It is shown that, assuming stabilizability and detectability of the individual systems and imposing very mild connectedness assumptions on the interconnection structure, an internal model requirement is necessary and sufficient for synchronizability of the network to polynomially bounded trajectories. The resulting dynamic feedback couplings can be interpreted as a generalization of existing methods for identical linear systems. 相似文献
8.
In this paper we adapt the AIC model selection rule to be used in combination with prior estimated noise models in the presence of model errors. It is shown that under these conditions a slightly modified cost function extension is needed, resulting in a multiplicative complexity term instead of an additive one as would be found for fixed noise models and no model errors. The equivalency of this result with the classical prediction error framework is discussed. 相似文献
9.
An algorithm is presented for reducing the number of terms in a nonlinear static system which can be modeled by a linear combination of nonlinear functions. The method is an improvement over a previously presented algorithm (Desrochers and Saridis, 1980a). The improvements now make it possible to perform all calculations from a single set of input and output data while in the original algorithm n sets of data were required where n is the number of terms retained. In addition, it is shown how the model error can be calculated at each iteration which relieves the arbitrariness of stopping the algorithm at a preselected value of n as was done originally. Then the insight gained from this improved technique is used to develop an optimal solution to the model reduction problem, a major improvement over the original technique. It is then conjectured that some structural concepts for such systems may exist in a matrix formed from the input and output data. 相似文献
10.
This study proposes a high-efficient approach to identify the piecewise affine (PWA) model. The proposed approach constitutes two major steps, initial estimation and refinement process. In the initial estimation, Hough Transform (HT) is adopted to generate a group of submodel candidates; then a variable-threshold technique is applied to pick up the real submodel. In the refinement process, not only the distance constraint between data points and submodel's hyperplanes but also the clustering constraint between data points in regression regions are considered. An efficient algorithm is presented to alternately refine the submodel's parameters and the subregression sets. In the case study, the proposed approach is used to identify the fault model of the track circuit in high-speed railway. Analysis shows that the proposed approach has linear time complexity and exhibits superior data availability in small-sample case. 相似文献
11.
针对煤矿井下光照变化较大、矿工脸部受污染及遮挡等情况下主动形状模型(ASM)应用于井下人脸跟踪精度低的问题,提出了一种改进ASM。首先选用专用的训练样本集,通过定义镜像图像形成镜像样本集,然后对镜像样本集进行对数尺度化处理,并用相关块模型作为ASM的学习模型进行训练。实验结果表明,改进ASM能有效提高煤矿井下人脸跟踪精度。 相似文献
12.
Powerlists are data structures that can be successfully used for defining parallel programs based on divide-and-conquer paradigm. These parallel recursive data structures and their algebraic theories offer both a methodology to design parallel algorithms and parallel programming abstractions to ease the development of parallel applications. The paper presents a technique for speeding up the parallel recursive programs defined based on powerlists. The improvements are achieved by applying transformation rules that introduce tuple functions and prefix operators, for which a more efficient execution model is defined. Together with the execution model, a cost model is also defined in order to allow a proper evaluation. The treated examples emphasise the fact that the transformation leads to important improvements of the programs. The speeding up is achieved by reducing the number of recursive calls, and also by enable the fusion of splitting/combining operations on different data structures. In addition, enhancing the function that has to be computed to other useful functions using a tuple, could improved the cost reduction even more. 相似文献
13.
In this paper, we present a new technique to address constrained robust model predictive control. The main advantage of this new approach with respect to other well-known techniques is the reduced conservativeness. Specifically, the technique described in this paper can be applied to polytopic uncertain systems and is based on the use of several Lyapunov functions each one corresponding to a different vertex of the uncertainty's polytope. 相似文献
14.
在线主题模型基于先时间离散后主题建模的思想,存在文本流切分带来的模型无法平滑过渡的问题,同时时间片大小的选择对在线话题的抽取质量影响显著。提出了一种新的在线短文本流主题演化模型Online-BTOT。模型在遗传计算方法上进行了改良,不仅考虑时间片上的总体主题强度对遗传权重的影响,也将时间片上主题强度的变化纳入先验参数的计算中。同时,为了得到主题强度在时间片上的连续变化和克服短文本的稀疏性,在单时间片上结合了TOT模型和BTM模型。通过在微博短文本语料上与OLDA模型和OBTM模型的对比实验,证明Online-BTOT模型能够有效地分析在线短文本流的主题演化。 相似文献
15.
In this paper, we suggest two kinds of approximation methods based on Taylor series expansion which can solve the non-linear equation in entropic lattice Boltzmann model without using any iteration methods such as Newton–Raphson method. The advantage of our methods is to be able to avoid the load imbalance in parallel computation which occurs due to the differences of iteration number on each calculation grid. In this study, ELBM simulations using our methods were compared with those using Newton–Raphson method for the channel flow past a square cylinder in Re = 1000 and the validity of the results and computational effort were investigated. As a result, it was found that the solutions obtained by our methods are qualitatively and quantitatively reasonable and CPU time is shorter than those obtained by Newton–Raphson method. 相似文献
16.
Multimedia Tools and Applications - Outdoor images lose color contrast and visibility in poor weather conditions (like fog, mist, haze and rain), which affects computer vision applications... 相似文献
17.
Presented is an improved three-dimensional display model of a human being which can be used to display the results of three-dimensional simulation programs that predict the positions of an occupant during impact of a vehicle. The model allows the user to view the occupant from any orientation in any position during the crash. The display model assumes the usual break up of the body into rigid segments, which is normal for occupant-crash simulation programs, but the shape of the segments in the display model are not necessarily the same as those used in the crash simulation. The display model is proportioned so as to produce a realistic drawing of the human body in any position. Joints connecting the seqments are also drawn to improve realism. 相似文献
18.
Preprocessing of data is ubiquitous, and choosing significant attributes has been one of the important steps in the prior processing of data. Feature selection is used to create a subset of relevant feature for effective classification of data. In a classification of high-dimensional data, the classifier usually depends on the feature subset that has been used for classification. The Relief algorithm is a popular heuristic approach to select significant feature subsets. The Relief algorithm estimates feature individually and selects top-scored feature for subset generation. Many extensions of the Relief algorithm have been developed. However, an important defect in the Relief-based algorithms has been ignored for years. Because of the uncertainty and noise of the instances used for measuring the feature score in the Relief algorithm, the outcome results will vacillate with the instances, which lead to poor classification accuracy. To fix this problem, a novel feature selection algorithm based on Chebyshev distance-outlier detection model is proposed called noisy feature removal-Relief, NFR-ReliefF in short. To demonstrate the performance of NFR-ReliefF algorithm, an extensive experiment, including classification tests, has been carried out on nine benchmarking high-dimensional datasets by uniting the proposed model with standard classifiers, including the naïve Bayes, C4.5 and KNN. The results prove that NFR-ReliefF outperforms the other models on most tested datasets. 相似文献
19.
随着移动互联网应用的不断普及,移动终端承载了大量的数据交互业务与应用,移动数据的安全问题日益凸显。基于C4.5决策树算法对移动数据进行文本分类检测,实现恶意代码分析。传统的C4.5文本分类模型中,测试属性选择未考虑属性之间的影响,因此提出了一种改进的基于Boosting算法的C4.5决策树文本分类模型。该模型在衡量被测属性最优弱假设的重要性时,引入Boosting的权重系数,每次迭代计算结束后,自适应调整权重值,在降低特征子集属性冗余度的同时,提高了分类模型的鲁棒性。实验结果表明,改进的文本分类模型在检测率和分类准确率上均有一定程度的提高。 相似文献
20.
An improved gas-damping model for the out-of-plane motion of a near-substrate microbeam is developed based on the Reynolds equation (RE). A boundary condition for the RE is developed that relates the pressure at the beam edge to the beam motion. The coefficients in this boundary condition are determined from Navier-Stokes slip-jump (NSSJ) simulations for small slip lengths (relative to the gap height) and from direct simulation Monte Carlo (DSMC) molecular gas dynamics simulations for larger slip lengths. This boundary condition significantly improves the accuracy of the RE when the microbeam width is only slightly greater than the gap height between the microbeam and the substrate. The improved RE model is applied to microbeams fabricated using the SUMMiT V process. 相似文献
|