抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

A heuristic method has been developed for registering two sets of 3-D curves obtained by using an edge-based stereo system, or two dense 3-D maps obtained by using a correlation-based stereo system. Geometric matching in general is a difficult unsolved problem in computer vision. Fortunately, in many practical applications, some a priori knowledge exists which considerably simplifies the problem. In visual navigation, for example, the motion between successive positions is usually approximately known. From this initial estimate, our algorithm computes observer motion with very good precision, which is required for environment modeling (e.g., building a Digital Elevation Map). Objects are represented by a set of 3-D points, which are considered as the samples of a surface. No constraint is imposed on the form of the objects. The proposed algorithm is based on iteratively matching points in one set to the closest points in the other. A statistical method based on the distance distribution is used to deal with outliers, occlusion, appearance and disappearance, which allows us to do subset-subset matching. A least-squares technique is used to estimate 3-D motion from the point correspondences, which reduces the average distance between points in the two sets. Both synthetic and real data have been used to test the algorithm, and the results show that it is efficient and robust, and yields an accurate motion estimate.

/pdf/iterative-point-matching-for-registration-of-free-form-5fl1ftde76.pdf

Iterative point matching for registration of free-form curves and surfaces

A scheme is developed for classifying the types of motion perceived by a humanlike robot. It is assumed that the robot receives visual images of the scene using a perspective system model. Equations, theorems, concepts, clues, etc., relating the objects, their positions, and their motion to their images on the focal plane are presented. >

http://ieeexplore.ieee.org/iel2/815/3148/00100651.pdf

Robot vision

Geometric matching in general is a difficult unsolved problem in computer vision. Fortunately, in many pratical applications, some a priori knowledge exists which considerably simplifies the problem. In visual navigation, for example, the motion between successive positions is usually either small or approximately known, but a more precise registration is required for environment modeling. The algorithm described in this report meets this need. Objects are represented by free-form curves, i.e., arbitrary spaces curves of the type found in practice. A curve is available in the form of a set of chained points. The proposed algorithm is based on iteratively matching points on one curve to the closest points on the other. A least-squares technique is used to estimate 3-D motion from the point correspondences, which reduces the average distance between curves in two sets. Both synthetic and real data have been used to test the algorithm, and the results show that it is efficient and robust, and yields an accurate motion estimate. The algorithm can be easily extended to solve similar problems such as 2-D curve matching and 3-D surface matching.

/pdf/iterative-point-matching-for-registration-of-free-form-b0pre910b7.pdf

Iterative point matching for registration of free-form curves

In many areas of industry, it is desirable to create geometric models of existing objects for which no such model is available. This paper reviews the process of reverse engineering of shapes. After identifying the purpose of reverse engineering and the main application areas, the most important algorithmic steps are outlined and various reconstruction strategies are presented. Pros and cons of various data acquisition techniques are described with related problems of boundary representation model construction. Specific issues addressed include characterization of geometric models and related surface representations, segmentation and surface fitting for simple and free-form shapes, multiple view combination and creating consistent and accurate B-rep models. The limitations of currently known solutions are also described, and we point out areas in which further work is required before reverse engineering of shape becomes a practical, widely-available engineering tool.

Reverse engineering of geometric models—an introduction

A Model Regulation approach for contol systems with significant uncertain dynamics is studied. The proposed approach regulates the behavior of the actual control plant to its nominal model so that desirable dynamic performance may be achieved by conventional controllers based on the nominal model in spite of the existence of significant uncertain dynamics. Analysis shows that the success of this approach is guaranteed in low frequency range and depends on the delay angle as well as the natural of the model uncertainty in high frquency range. The stability of the compensated system is also determined by the delay angle and the model uncertainty. A DC servomotor system is chosen as an example to demonstrate the effectiveness of the proposed approach. Computer simulations and experimental results prove that both linear (payload variation) and nonlinear (friction force) uncertain dynamics are compensated by the model regulation approach.

https://ieeexplore.ieee.org/iel5/4791998/4791999/04792753.pdf

Discrete Model Regulation for Systems with Uncertain Dynamics

Identification and Characterization of Regular Surfaces from Unorganized Points by Normal Sensitivity Analysis

In this paper, the effect of the reference misalignment on the tooth measurements of an involute spur gear is examined. Analytical relations between the profile/lead traces and the reference misalignment parameters are derived. These relations can be employed to estimate the misalignment parameters when three or more profile and lead traces are available. The estimated parameters may be subsequently used to remove the effect of the reference misalignment on the profile and lead traces. Experiments are conducted to verify the proposed method and to illustrate the applications of the developed approach.

Estimation of Reference Misalignment of a Spur Gear and its Application to Profile and Lead Measurement

This article presents the optimal current allocation and the magnetic force production associated with the hexapole electromagnetic actuation, wherein six electromagnets are used to control the magnetic field and exert the 3-D magnetic force on a specified microscopic magnetic particle in the 3-D workspace of the actuating system. It addresses four major issues in the inverse modeling of the multipole electromagnetic actuation, i.e., 1) redundancy; 2) coupling; 3) nonlinearity; and 4) position-dependency, and leads to the accurate and effective 3-D magnetic force production within the specified workspace. Specifically, the optimal inverse modeling of the hexapole electromagnetic actuation is derived to minimize the 2-norm of the $6 \times 1$ input current vector when applied to produce the desired 3-D magnetic force to propel the magnetic particle in aqueous solutions. The inverse model is implemented in a high-speed field programmable gate array system to realize the real-time current allocation, which is used to render the feedback stabilization of the magnetic trap. The accurate and effective 3-D force production through the optimal current allocation is experimentally validated.

Optimal Current Allocation Rendering 3-D Magnetic Force Production in Hexapole Electromagnetic Actuation

The nine papers in this special section focus on precision actuators, precision sensors, novel maglev systems, and precision control of electromagnetic systems.

/pdf/guest-editorial-introduction-to-the-focused-section-on-4bjeobjteg.pdf

Chia-Hsiang Menq

Papers

Discrete Model Regulation for Systems with Uncertain Dynamics

Identification and Characterization of Regular Surfaces from Unorganized Points by Normal Sensitivity Analysis

Estimation of Reference Misalignment of a Spur Gear and its Application to Profile and Lead Measurement

Optimal Current Allocation Rendering 3-D Magnetic Force Production in Hexapole Electromagnetic Actuation

Guest Editorial Introduction to the Focused Section on Electromagnetic Devices for Precision Engineering