A DFO technique to calibrate queueing models

A crucial step in the modeling of a system is to determine the values of the parameters to use in the model. In this paper we assume that we have a set of measurements collected from an operational system, and that an appropriate model of the system (e.g., based on queueing theory) has been developed. Not infrequently proper values for certain parameters of this model may be difficult to estimate from available data (because the corresponding parameters have unclear physical meaning or because they cannot be directly obtained from available measurements, etc.). Hence, we need a technique to determine the missing parameter values, i.e., to calibrate the model.As an alternative to unscalable “brute force” technique, we propose to view model calibration as a non-linear optimization problem with constraints. The resulting method is conceptually simple and easy to implement. Our contribution is twofold. First, we propose improved definitions of the “objective function” to quantify the “distance” between performance indices produced by the model and the values obtained from measurements. Second, we develop a customized derivative-free optimization (DFO) technique whose original feature is the ability to allow temporary constraint violations. This technique allows us to solve this optimization problem accurately, thereby providing the “right” parameter values. We illustrate our method using two simple real-life case studies.     

A 1-Local Asymptotic 13/9-Competitive Algorithm for Multicoloring Hexagonal Graphs

In the frequency allocation problem, we are given a mobile telephone network, whose geographical coverage area is divided into cells, wherein phone calls are serviced by assigning frequencies to them so that no two calls emanating from the same or neighboring cells are assigned the same frequency. The problem is to use the frequencies efficiently, i.e., minimize the span of frequencies used. The frequency allocation problem can be regarded as a multicoloring problem on a weighted hexagonal graph. In this paper, we give a 1-local asymptotic 4/3-competitive distributed algorithm for multicoloring a triangle-free hexagonal graph, which is a special case of hexagonal graph. Based on this result, we then propose a 1-local asymptotic13/9-competitive algorithm for multicoloring the (general-case) hexagonal graph, thereby improving the previous 1-local 3/2-competitive algorithm. A preliminary version of this paper appeared in the Proceedings of the 13th Annual International Computing and Combinatorics Conference (COCOON 2007), LNCS 4598, pp. 526–536. Y. Zhang research was supported by European Regional Development Fund (ERDF). F.Y.L. Chin research was supported by Hong Kong RGC Grant HKU-7113/07E. H. Zhu research was supported by National Natural Science Fund (grant #60496321).     

A Visualization Based Approach for Digital Signature Authentication

We propose a visualization based approach for digital signature authentication. Using our method, the speed and pressure aspects of a digital signature process can be clearly and intuitively conveyed to the user for digital signature authentication. Our design takes into account both the expressiveness and aesthetics of the derived visual patterns. With the visual aid provided by our method, digital signatures can be authenticated with better accuracy than using existing methods—even novices can examine the authenticity of a digital signature in most situations using our method. To validate the effectiveness of our method, we conducted a comprehensive user study which confirms positively the advantages of our approach. Our method can be employed as a new security enhancement measure for a range of business and legal applications in reality which involve digital signature authorization and authentication.     

Improved Interface Conditions for 2<Emphasis Type="Italic">D</Emphasis> Domain Decomposition with Corners: Numerical Applications

This article deals with a local improvement of domain decomposition methods for 2-dimensional elliptic problems for which either the geometry or the domain decomposition presents conical singularities. After explaining the main results of the theoretical analysis carried out in Chniti et al. (Calcolo 45, 2008), the numerical experiments presented in this article confirm the optimality properties of the new interface conditions.     

Control of an industrial copper solvent extraction process

A two level control strategy that stabilizes and optimizes the production of an industrial copper solvent extraction process is presented. The stabilizing layer consists of a multi-input–multi-output controller or two single-input–single-output controllers with additional four feedforward compensators that regulate the flow rates in the copper solvent extraction process. The optimization layer consists of an optimizer that maximizes the production of the copper solvent extraction process and gives setpoints to the controllers at the stabilizing level. The mechanistic plant models, verified with industrial data, are linearized by identifying first and higher order transfer function models from simulated PRBS data. On the basis of the linear models, the interactions of the controlled variables, and the pairing of the controlled and manipulated variables are studied and the optimizer and the controllers designed. The control strategy employing two PI-control loops or a model predictive controller and additionally four feedforward control loops is successfully tested against simulated disturbances and setpoint changes. The control strategy is also compared to the data collected from the industrial plant under manual control. With this two level control strategy the production of the copper solvent extraction process is increased by 3–5% and the process variation is decreased by 70–90% compared to the manual operation of the case industrial plant. The results gained in simulation environment are successful and encouraging for further testing in an industrial plant.     

A faster branch-and-bound algorithm for the earliness-tardiness scheduling problem

This paper addresses the one-machine scheduling problem with earliness-tardiness penalties. We propose a new branch-and-bound algorithm that can solve instances with up to 50 jobs and that can solve problems with even more general non-convex cost functions. The algorithm is based on the combination of a Lagrangean relaxation of resource constraints and new dominance rules.     

Olfactory Responses to Aphid and Host Plant Volatile Releases: (E)-β-Farnesene an Effective Kairomone for the Predator Adalia bipunctata

The volatiles released from several aphid and host plant species, alone or associated, were studied for their infochemical role in prey location. Using a four-arm olfactometer, the attraction of several combinations of three aphid (Myzus persicae, Acyrthosiphon pisum, and Brevicoryne brassicae) and three plant (Vicia faba, Brassica napus, and Sinapis alba) species toward Adalia bipunctata larvae and adults was observed. Both predatory larvae and adults were attracted only by A. pisum and M. persicae when they were crushed, whatever the host plant. (E)-beta-farnesene, the aphid alarm pheromone, was the effective kairomone for the ladybird. Plant leaves alone (V. faba, B. napus, and S. alba) or in association with nonstressed whole aphids (the three species) did not have any attraction for the predator. The B. brassicae specialist aphid is the only prey that was not attracted to A. bipunctata larvae and adults, even if they were crushed. Release of B. brassicae molecules similar to the host plant allelochemicals was demonstrated by GC-MS analysis. The lack of behavioral response of the ladybird at short distance toward the cruciferous specialist aphid was related only to the absence of (E)-beta-farnesene in the aphid prey volatile pattern.     

Systems interface biology.

The field of systems biology has attracted the attention of biologists, engineers, mathematicians, physicists, chemists and others in an endeavour to create systems-level understanding of complex biological networks. In particular, systems engineering methods are finding unique opportunities in characterizing the rich behaviour exhibited by biological systems. In the same manner, these new classes of biological problems are motivating novel developments in theoretical systems approaches. Hence, the interface between systems and biology is of mutual benefit to both disciplines.     

Maternal influences on daughters' restrained eating behavior.

This study examined whether mothers' preoccupation with their own weight and eating was linked to daughters' restrained eating behavior. Participants included 173 non-Hispanic, White mother-daughter dyads, measured longitudinally when daughters were ages 5, 7, 9, and 11. Mothers who were preoccupied with their own weight and eating reported higher levels of restricting daughters' intake and encouraging daughters to lose weight over time. Mothers' encouragement of daughters' weight loss was linked to daughters' restrained eating behavior; this relationship was partially mediated by daughters' perception of maternal pressure to lose weight. These findings suggest that mothers' preoccupation with weight and eating, via attempts to influence daughters' weight and eating, may place daughters at risk for developing problematic eating behaviors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Is the Internet going NUTSS?

For nearly 10 years now, the Internet Architecture Board (IAB) and Internet Engineering Task Force (IETF) have been telling us that the pool of available IP addresses will soon be exhausted, and that Internet growth will come to a grinding halt. They have heavily promoted their solution, IPv6, which the commercial world has all but ignored. It is now becoming clear that IP address exhaustion is years off, at best. The primary reason for this is network address translation (NAT), the rogue technology that allows almost unlimited address reuse. Despite NAT's nagging technical problems that limit IP connectivity and make peer-to-peer (P2P) applications difficult to deploy, the commercial world has universally embraced the technology even as the IAB and IETF actively discourage its use.