A hybrid surrogate and pattern search optimization method and application to microelectronics

A hybrid method for robust and efficient optimization process is developed by integrating a new response surface method and pattern search algorithm. The method is based on: (1) multipoint approximations of the objective and constraint functions, (2) a multiquadric radial basis function (RBF) for the zeroth-order function approximation and a new RBF plus polynomial-based moving least-squares approximation for the first-order enhanced function approximation, and (3) a pattern search algorithm to impose a descent condition and applied adaptive subregion management strategy. Several numerical examples are presented to illustrate accuracy and computational efficiency of the proposed method for both function approximation and design optimization. To demonstrate the effectiveness of the proposed hybrid method, it is applied to obtain optimum designs of a microelectronic packaging system. A two-stage optimization approach is proposed for the design optimization. The material properties of microelectronic packaging system and the shape parameters of solder ball are selected as design variables. Through design optimization, significant improvements of durability performances are obtained using the proposed hybrid optimization method.     

Partial correlation with copula modeling

We propose a new partial correlation approach using Gaussian copula. Our empirical study found that the Gaussian copula partial correlation has the same value as that which is obtained by performing a Pearson’s partial correlation. With the proposed method, based on canonical vine and d-vine, we captured direct interactions among eight histone genes.     

Surface slope effects on shingling frequency and postural balance in a simulated roofing task

The purpose of this study was to investigate the influence of surface slopes (18 degrees , 26 degrees , 34 degrees ) on the maximum acceptable roof shingling frequency for males performing a simulated roof-shingling task. The psychophysical roof shingling frequency was also compared to the postural sway and trunk motion values. The maximum acceptable roof shingling frequency and selected trunk motion decreased significantly with an increase in slope. Postural sway however increased significantly with an increase in slope. The study also revealed that workers were experiencing a greater postural sway at the earlier phase of task on the steeper surface. This suggests that there might be an adaptation period associated with working on a slope and the body's ability to compensate for a loss of balance. Therefore, more emphasis should be given to the workers in this adaptation period, with additional monitoring and cautionary measures. Collectively, the findings of the study could be utilized for improving work practices on roofs, while reducing the potential risks of falls in roofing construction.     

EM-GPA: Generalized Procrustes analysis with hidden variables for 3D shape modeling

Aligning shapes is essential in many computer vision problems and generalized Procrustes analysis (GPA) is one of the most popular algorithms to align shapes. However, if some of the shape data are missing, GPA cannot be applied. In this paper, we propose EM-GPA, which extends GPA to handle shapes with hidden (missing) variables by using the expectation-maximization (EM) algorithm. For example, 2D shapes can be considered as 3D shapes with missing depth information due to the projection of 3D shapes into the image plane. For a set of 2D shapes, EM-GPA finds scales, rotations and 3D shapes along with their mean and covariance matrix for 3D shape modeling. A distinctive characteristic of EM-GPA is that it does not enforce any rank constraint often appeared in other work and instead uses GPA constraints to resolve the ambiguity in finding scales, rotations, and 3D shapes. The experimental results show that EM-GPA can recover depth information accurately even when the noise level is high and there are a large number of missing variables. By using the images from the FRGC database, we show that EM-GPA can successfully align 2D shapes by taking the missing information into consideration. We also demonstrate that the 3D mean shape and its covariance matrix are accurately estimated. As an application of EM-GPA, we construct a 2D + 3D AAM (active appearance model) using the 3D shapes obtained by EM-GPA, and it gives a similar success rate in model fitting compared to the method using real 3D shapes. EM-GPA is not limited to the case of missing depth information, but it can be easily extended to more general cases.     

Leakage Minimization Technique for Nanoscale CMOS VLSI

Because of the continued scaling of technology and supply-threshold voltage, leakage power has become more significant in power dissipation of nanoscale CMOS circuits. Therefore, estimating the total leakage power is critical to designing low-power digital circuits. In nanometer CMOS circuits, the main leakage components are the subthreshold, gate-tunneling, and reverse-biased junction band-to-band-tunneling (BTBT) leakage currents.     

Robust measurement of ocular torsion using iterative Lucas-Kanade

We present a new method to measure ocular torsion using Lucas-Kanade method. After pixels of iris annulus around a pupil have been converted into Cartesian coordinates, 30 features on the iris was selected then the features were tracked using the iterative Lucas-Kanade algorithm to calculate torsional shift. The results show that a precision of the method is higher than those measured by a conventional cross-correlation and by a template matching method. The suggested method showed 0.03 degrees mean error with 0.15 degrees maximum error. Particularly, the method was robust to change of pupil size and misalignment of pupil location. Processing time was also fast enough to be implemented in a real-time system.     

Implementation issues in RFID-based anti-counterfeiting systems

RFID has emerged as a potential tool to combat product counterfeiting, which undermines the global economy hugely. Recently, a number of anti-counterfeiting approaches have been proposed for such purpose. This paper presents a track-and-trace system for RFID-based anti-counterfeiting, and addresses possible implementation issues, such as tag selection, product tagging, tag programming and locking. A packaging line for bottled products is developed and integrated with the proposed system for investigation of these issues. Experiments are conducted to determine the critical tag moving speed beyond which the tag programming rate or reliability of tagged products being transferred on a convey drops significantly. The critical tag moving speed is vital not only for determining the maximum production throughput possible, but also for setting up RFID equipment needed to ensure tagged products with erroneous tagging can be sorted out from the packaging line accordingly.     

Maximizing the weighted number of just-in-time jobs in flow shop scheduling

In this paper we consider the maximization of the weighted number of just-in-time jobs that should be completed exactly on their due dates in n-job, m-machine flow shop problems. We show that a two-machine flow shop problem is NP-complete. When job weights are all identical, we show that the problem can be solved in polynomial time. We also show that a three-machine flow shop problem with identical job weights is NP-hard in the strong sense by reduction of the 3-partition problem.     

Dynamics modeling and analysis of a biped walking robot actuated by a closed-chain mechanism

We developed a new type of human-sized biped walking robot (BWR) driven by the closed-chain type of joint actuator. Each leg of the robot is composed of three pitch joints and one roll joint. In all, a 15 degree-of-freedom robot including four arm joints and three joints for the head was developed. The BWR was developed to walk autonomously such that all leg joints are actuated by small 90 W dc motors/drivers and dc batteries and controllers which are boarded. The joint actuator for the BWR is composed of the four-bar-link mechanism driven by the ball screw which has high strength and high gear ratio. A dynamics modeling of the developed BWR for forward walking is presented in which the revolute joint dynamics are transformed into the prismatic joint dynamics of the ball screw. Also, an analysis on the four-bar-link mechanism applied to the joint actuator and on the structure of the BWR is shown. The design specification of the actuating motor for the BWR is analyzed through the torque analysis of the four-bar-link actuator. Through walking experiments of the BWR, the walking performance and trajectory tracking ability is shown. © 2004 Wiley Periodicals, Inc.     

Improved Controller Design with Two Gain-scaling Factors for Global Asymptotic Stabilization of Nonlinear Systems via Matrix Inequality Approach

In this paper, we consider a problem of global asymptotic stabilization for nonlinear systems with the perturbed nonlinearity. We provide a stabilizing controller with two gain-scaling factors and a new controller design method with matrix inequality approach. In particular, we provide a new procedure for selecting gain-scaling factors which are associated with stabilizing the closed-loop system. As a result, our proposed control method widens the class of considered nonlinear systems and yields better control performance over the existing methods. Via several comparison examples, we illustrate the improved features of the proposed control method over the existing ones.