Position synchronization of multiple motion axes with adaptive coupling control

A new control approach to position synchronization of multiple motion axes is developed, by incorporating cross-coupling technology into adaptive control architecture. The control strategy is to stabilize position tracking of each axis while synchronizing its motion with other axes’ motions so that differential position errors amongst axes converge to zero. The proposed adaptive controller and parameter estimator employ coupling control by feeding back position errors and differential position errors, and have been realized to guarantee asymptotic convergence to zero of both position and synchronization errors. Simulations conducted on a multi-axis motion control system demonstrate the effectiveness of the method.     

Level set and geodesic active contours based measurement of material removal between serial sections

The measurement of the thickness of material removed between serial sections is a crucial step of three-dimension reconstruction. Geodesic active contours is an efficient method for contour detection of objects on an image. The indents on the SiC/Al composite micrographs are segmented by using level set and geodesic active contours. After getting the contours of the indents, we calculate the distance from the uppermost pixel to the lowermost pixel to get the vertical diagonal length, and calculate the distance from the leftmost pixel to the rightmost pixel to get the horizontal diagonal length of each contour. Then the final length of each diagonal is acquired by averaging the vertical diagonal length and the horizontal diagonal length, respectively. The Vickers’ indenter is made by a square pyramidal-shaped diamond with opposite faces at an angle of 136°, so the thickness of material removed between two serial sections and the length difference of the diagonals on the two serial sections has a definite geometrical relation. Thus the thickness of material removed between two serial sections is acquired using the geometrical relation.     

中间馏分油型加氢裂化催化剂用沸石的研究

通过水热处理法制备了3个不同脱铝深度的改性Y沸石，再经浸渍法制成中间馏分油型加氢裂化催化剂，在200mL小型加氢裂化装置上进行了催化性能评价。试验结果表明，除了沸石的酸性外，其孔结构和比表面积对催化剂的活性、中间馏分油选择性和液体收率都有很大的影响，为最大幅度提高催化剂的中间馏分油选择性并保持较好活性，要求沸石具有较低的酸量、较高的比表面积和较多的二次孔及适量的L酸量。     

Nonlinear model predictive control with polytopic invariant sets

Ellipsoidal invariant sets have been widely used as target sets in model predictive control (MPC). These sets can be computed by constructing appropriate linear difference inclusions together with additional constraints to ensure that the ellipsoid lies within a given inclusion polytope. The choice of inclusion polytope has a significant effect on the size of the target ellipsoid, but the optimal inclusion polytope cannot in general be computed systematically. This paper shows that use of polytopic invariant sets overcomes this difficulty, allowing larger stabilizable sets without loss of performance. In the interests of online efficiency, consideration is focused on interpolation-based MPC.     

Frequency domain solution to delay-type Nehari problem

This paper generalizes the frequency-domain results on the delay-type Nehari problem in the stable case to the unstable case. The solvability condition of the delay-type Nehari problem is formulated in terms of the nonsingularity of three matrices. The optimal value γ_opt is the maximal γ∈(0,∞) such that one of the three matrices becomes singular. All sub-optimal compensators are parameterized in a transparent structure incorporating a modified Smith predictor.     

EM procedures using mean field-like approximations for Markov model-based image segmentation

Image segmentation using Markov random fields involves parameter estimation in hidden Markov models for which the EM algorithm is widely used. In practice, difficulties arise due to the dependence structure in the models and approximations are required. Using ideas from the mean field approximation principle, we propose a class of EM-like algorithms in which the computation reduces to dealing with systems of independent variables. Within this class, the simulated field algorithm is a new stochastic algorithm which appears to be the most promising for its good performance and speed, on synthetic and real image experiments.     

Determination of vitality from a non-invasive biomedical measurement for use in fingerprint scanners

Fingerprints are the oldest and most widely used biometrics for personal identification. Unfortunately, it is usually possible to deceive automatic fingerprint identification systems by presenting a well-duplicated synthetic or dismembered finger. This paper introduces one method to provide fingerprint vitality authentication in order to solve this problem. Detection of a perspiration pattern over the fingertip skin identifies the vitality of a fingerprint. Mapping the two-dimensional fingerprint images into one-dimensional signals, two ensembles of measures, namely static and dynamic measures, are derived for classification. Static patterns as well as temporal changes in dielectric mosaic structure of the skin, caused by perspiration, demonstrate themselves in these signals. Using these measures, this algorithm quantifies the sweating pattern and makes a final decision about vitality of the fingerprint by a neural network trained by examples.     

硝酸处理对MgCr_2O_4-Bi_2O_3陶瓷湿敏元件性能的影响

报道了硝酸老化处理方法对MgCr_2O_4—Bi_2O_3陶瓷湿敏元件的结构和性能的影响。实验结果表明,硝酸老化处理不仅是一种可行的造孔方法,而且对元件的力学和电学性能有重要影响。用浓度适宜的硝酸处理后,会得到性能较好的元件。