Knowledge-based acquisition of tradeoff preferences for negotiating agents A wide range of algorithms have been developed for various types of automated negotiation. In developing such algorithms the main focus has been on their efficiency and their effectiveness. However, this is only part of the picture. Agents typically negotiate on behalf of their owners and for this to be effective the agent must be able to adequately represent the owners' preferences. However, the process by which such knowledge is acquired is typically left unspecified. To remove this shortcoming, we present a case study indicating how the knowledge for a particular negotiation algorithm can be acquired. More precisely, according to the analysis on the automated negotiation model, we identified that user trade-off preferences play a fundamental role in negotiation in general. This topic has been addressed little in the research area of user preference elicitation for general decision making problems as well. In a previous paper, we proposed an exhaustive method to acquire user trade-off preferences. In this paper, we developed another method to remove the limitation of the high user workload of the exhaustive method. 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O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O 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Exponential-time approximation of weighted set cover The Set Cover problem belongs to a group of hard problems which are neither approximable in polynomial time (at least with a constant factor) nor fixed parameter tractable, under widely believed complexity assumptions. In recent years, many researchers design exact exponential-time algorithms for problems of that kind. The goal is getting the time complexity still of order O(c n ), but with the constant c as small as possible. In this work we extend this line of research and we investigate whether the constant c can be made even smaller when one allows constant factor approximation.In fact, we describe a kind of approximation schemes -trade-offs between approximation factor and the time complexity. We use general transformations from exponentialtime exact algorithms to approximations that are faster but still exponential-time. For example, we show that for any reduction rate r, one can transform any O * (c n )-time 1 algorithm for Set Cover into a (1 + ln r)-approximation algorithm running in time O * (c n/r ). We believe that results of that kind extend the applicability of exact algorithms for NPhard problems. One way of coping with NP-hardness is polynomial-time approximation, i.e. looking for solutions that are relatively close to optimal. Unfortunately it turns out that there are still many problems which do not allow for good approximation. Let us recall some examples. Håstad [14] showed that Independent Set cannot be approximated in polynomial time with factor n 1− for any > 0 unless NP = ZPP. The same holds for Vertex Coloring due to Feige and Kilian [11] . By another result of Feige [10] , Set Cover cannot be approximated in polynomial time with factor (1 − ) ln n, where n is the size of the set to cover, for any > 0 unless NP ⊆ DTIME(n log log n ).. Another approach is the area of parametrized complexity (see e.g. [9] ). Then the goal is to find an algorithm with time exponential only in a parameter unrelated to the instance size (then we say the problem is fixed parameter tractable, FPT in short). This parameter may reflect complexity of the instance -like treewidth, but then we get an efficient algorithm only for some subclass of possible instances. Another choice of the parameter is the measure of the solution quality. For example, one can verify whether in an n-vertex graph there is a vertex cover of size k in O(1.2738 k + kn) time [6] . Again, the parametrized approach does not succeed in some cases. Verifying whether a graph is k-colorable is NP-complete for any k ≥ 3, while Independent Set and Set Cover are W [1]-and W [2]-complete respectively, meaning roughly that an FPT algorithm for Independent Set or Set Cover would imply algorithms of that kind for a host of other hard problems.. The aforementioned hardness results motivate the study of "moderately exponential time" algorithms. The goal here is to devise algorithms with exponential running time O(2 n/r ) with r big enough. Indeed, a O(2 n/50 )-time algorithm may appear practical for some range of n, say n ≤ 1000. Despite some progress in this area we are still far from exact algorithms with time complexity of that order. One of the most researched problems in this field is Independent Set. Exhaustive search for that problem gives O(2 n ) time bound while the currently best published result [12] is O(2 n/3.47 ). For Vertex Coloring the first O * (2 n/0.77 )-time algorithm by Lawler was then improved in a series of papers culminating in a breakthrough O * (2 n ) bound of Björklund, Husfeldt and Koivisto [3] . Now consider the (weighted) Set Cover problem. The instance consists of a family of sets S = {S 1 , . . . , S m }, and each of the sets S i is assigned a weight w(S i ). The set U = S is called the universe and we denote n = |U |. The goal is to find a subfamily C ⊆ S such that C = U so as to minimize the total weight of the sets in C. Assume that the size of our instance is relatively small but big enough that finding an optimal solution using an exact algorithm is out of question, say m = 150, n = 200. If we use the (best known) greedy approximation algorithm (see e.g. [18] ), we get the approximation ratio of H n < ln n + 1, which is roughly 6.3 in this case. A simple implementation of this algorithm runs in O((. time, so we would get an answer very fast. A natural question is: can we get a better approximation guarantee by investing more computing time? Motivated by this question we look for approximation algorithms with good (e.g. constant) approximation guarantee and with running time exponential but substantially lower than the best known exact algorithm. Ideally, one would like to have a kind of trade-off between the running-time and approximation ratio -then one gets as much accuracy as one can afford. The concept of algorithms with a trade-off between the approximation ratio and the runningtime is quite old, though researchers focused on polynomial-time algorithms -so called polynomial-time approximation schemes (PTAS). Probably one of the earliest and most widely known examples of this kind is the PTAS for the knapsack problem, due to Ibarra and Kim [15] , which has approximation ratio of (1 − ε) and time complexity O(n 3 /ε), for any ε > 0. For more examples of PTASes see the textbook of Vazirani [18] .. The first work on exponential-time approximation algorithms we are aware of concerns the Max Sat problem and it is due to Dantsin, Gavrilovich, Hirsch and Konev [8] .. Later, Björklund and Husfeldt in [2] showed that any O * (c n )-time algorithm for the vertex coloring problem can be transformed into a (1+ln r)-approximation algorithm running in time O * (c n/r + 1.2209 n ). In a way, they also use the method of reduction and this is probably the first application of this method in exponential-time approximation.. Very recently, exponential-time approximation algorithms for Set Cover were studied by Bourjeois, Escoffier and Paschos [5] . Independently, they used a very similar approach to ours, and they obtained approximation algorithms with the same performance as the two algorithms we present here. Additionally, they show a randomized r-approximation algorithm with time complexity smaller (by an exponential factor) than O * (2 m/r ) that returns the correct answer with high probability. However, all their algorithms apply to unweighted version of the problem only and do not extend directly to the weighted version we consider here.. The same team investigated also exponential-time approximation algorithms for Independent Set and Vertex Cover, see [4] , getting some interesting results (also using the reduction, among other methods).. The idea of joining the worlds of approximation algorithms and "moderately" exponential algorithms appeared also in a recent work of Vassilevska, Williams and Woo [17] . However their direction of research is completely different from ours, i.e. they consider so-called hybrid algorithms. For example, they report to have an algorithm for bandwidth which for given input either returns an O(log n)-approximate solution in polynomial time or returns a (1 + )-approximate solution in O(2 n/ log log n ) time. We see that the hybrid algorithm does not guarantee constant approximation ratio and hence cannot be directly compared with our work.. Another promising area is joining the worlds of parametrized complexity and polynomialtime approximation algorithms -see the survey paper [16] .

O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O


Practical and Incremental Maintenance of Software Resources in Consumer Electronics Products We introduce a method, so called FC method, for maintaining software resources, such as source codes and design documents, in consumer electronics products. Because a consumer electronics product is frequently and rapidly revised, software components in such product are also revised in the same way. However, it is not so easy for software engineers to follow the revision of the product because requirements changes for the product, including the changes of its functionalities and its hardware components, are largely independent of the structure of current software resources. FC method lets software engineers to restructure software resources, especially design documents, stepwise so as to follow the requirements changes for the product easily. We report an application of this method in our company to validate it. From the application, we can confirm that the quality of software was improved about in twice, and that efficiency of development process was also improved over four times. Traditionally, software components in a consumer electronics product are designed so as to correspond to tasks in the product, and the components are implemented by each software engineer. The reasons are as follows. First, software components should contribute to make full use of hardware components, and the tasks normally correspond to hardware components. Second, software design method based on the tasks seems to be one of the best ways to do so. As a result, existing software components can not be easily modified if hardware components in the products are changed. Unfortunately, such hardware components are frequently changed along with the revision of the consumer electronics products today. Therefore, software design method based on tasks becomes unfit for embedded software in consumer electronics products today. If such method is used continuously, software resources e.g., source codes and design documents, become unmanageable. As a result, software engineers cannot understand and update existing software components correctly and efficiently.. In this paper, we will propose a new design method, FC (Functional Component) method, to overcome such problems, and report an experience to apply the method into a real software project. In FC method, software requirements Manuscript received September 24, 2004 . Manuscript revised January 4, 2005 . † The author is with EPSON AVASYS Corporation, Ueda-shi, 386-1214 Japan.. † † The authors are with the Graduate School of Science and Technology, Shinshu University, Nagano-shi, 380-8553 Japan.. a) E-mail: kaiya@cs.shinshu-u.ac.jp DOI: 10.1093/ietisy/e88-d. 6.1117 are decomposed into functional components, each of which is independent to specific hardware components. FC method also lets software engineers to make full use of existing software resources. Through the experience, we found that FC method helped software engineers to revise an existing software product effectively and efficiently. We also found that the number of defects decreased in about half, and that the average effort for review was decreased in about one fourth. The rest of this paper is organized as follows. In the next section, we clarify usual practice for developing embedded software in consumer electronics products, and its problems. So as to resolve several parts of the problems, we introduce FC method in Sect. 3. We applied FC method into practice and compared the results with results of usual practice. In Sect. 4 , we report such practices and discuss the differences to validate FC method. In Sect. 5, we discuss the characteristics of our work related to the other research results. Finally, we summarize current results and show the future works. There are many kinds of products with embedded software, and a consumer electronics product is one of the important product today. The characteristics of the product were summarized in [8] about ten years ago, and they are still true now. In this section, we discuss related works with respect to several viewpoints.

O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


The best keying protocol for sensor networks Many sensor networks (especially networks of mobile sensors or networks that are deployed to monitor crisis situations) are deployed in an arbitrary and unplanned fashion. Thus, any sensor in such a network can end up being adjacent to any other sensor in the network. To secure the communications between every pair of adjacent sensors in such a network, each sensor x in the network needs to store n − 1 symmetric keys that sensor x shares with all the other sensors, where n is an upper bound on the number of sensors in the network. This storage requirement of the keying protocol is rather severe, especially when n is large and the available storage in each sensor is modest. Earlier efforts to redesign this keying protocol and reduce the number of keys to be stored in each sensor have produced protocols that are vulnerable to impersonation, eavesdropping, and collusion attacks. In this paper, we present a fully secure keying protocol where each sensor needs to store (n + 1)/2 keys, which is much less than the n − 1 keys that need to be stored in each sensor in the original keying protocol. We also show that in any fully secure keying protocol, each sensor needs to store at least (n − 1)/2 keys. Typically, each sensor in a sensor network with n sensors needs to store n − 1 shared distinct (in order to ensure that the keying protocol is collusion-proof) symmetric keys to communicate securely with each other. Thus, the number of shared symmetric keys stored in the sensor network is n(n − 1). However, the optimal number of shared symmetric keys for secure communication, theoretically, is  n 2  = n(n − 1)/2. Although there have been many approaches that attempt to reduce the number of shared symmetric keys, they lead to a loss of security: they are all vulnerable to collusion. In this paper, we show the best keying protocol for sensor networks, that needs to store only (n + 1)/2 shared symmetric keys to each sensor. The number of shared symmetric keys stored in a sensor network with n sensors is n(n + 1)/2, which is close to the optimal number of shared symmetric keys for any key distribution scheme that is not vulnerable to collusion. It may be noted that in addition to the low number of keys stored, and the ability to resist collusion between sensors, our keying protocol has two further advantages. Firstly, it is uniform: we store the same number of keys in each sensor. Secondly, it is computationally cheap, and thus suitable for a low-power computer such as a sensor: when two sensors are adjacent to each other, the computation of a shared symmetric key requires only hashing, which is a cheap computation and can be done fast. As our protocol has many desirable properties, such as efficiency, uniformity and security, we call this protocol the best keying protocol for sensor networks.

O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O B I O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O B I O B O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O


On the stability of bubble functions and a stabilized mixed finite element formulation for the Stokes problem Abstract. In this paper we investigate the relationship between stabilized and enriched finite element formulations for the Stokes problem. We also present a new stabilized mixed formulation for which the stability parameter is derived purely by the method of weighted residuals. This new formulation allows equal order interpolation for the velocity and pressure fields. Finally, we show by counterexample that a direct equivalence between subgrid-based stabilized finite element methods and Galerkin methods enriched by bubble functions cannot be constructed for quadrilateral and hexahedral elements using standard bubble functions. It is well known that under the mixed Galerkin formulation for the Stokes problem many practically convenient combinations of interpolation functions for the velocity and pressure fields often do not yield stable results. In particular, equal order interpolation for velocity and pressure (which is computationally the most convenient) is not stable. This numerical instability is attributed to the lack of stability in the pressure field which is mathematically explained by the celebrated Ladyzhenskaya-Babuška-Brezzi (LBB) stability condition [1] . One can verify the LBB condition numerically by means of a well designed patch test.. To address the deficiencies in the classical mixed formulation of the Stokes equations, two classes have emerged grouped by similar methodologies: stabilized finite element methods and enriched finite element methods. By stabilized finite element methods we mean methods that add mesh dependent terms to the standard Galerkin formulation that enable the formulation to satisfy or circumvent the LBB condition [2] . In contrast, enriched finite element methods add bubble functions to the finite element function space, which in turn play a stabilizing role.. construct an equivalence between stabilized methods and bubble enrichment methods for these elements.. The rest of this paper is organized as follows. First we present a consistent stabilized formulation for which the stability parameter is constructed from the element residual. Next, we propose an alternative residual based formulation that can be derived purely by the method of weighted residuals. Lastly, we present a mathematically equivalent enriched formulation and show that whereas the stabilized formulation does not show spurious pressure oscillations for a given test problem, the enriched formulation does. We conclude with some remarks regarding the equivalence between stabilized and enriched finite element methods for the Stokes problem. We have introduced a new stabilized formulation for the Stokes problem that is appropriate for equal order interpolation for the velocity and pressure fields. The new formulation produces a scalar stabilization parameter that is consistently derived purely by the method of weighted residuals. We have also shown that an equivalence between enriched finite element methods and stabilized methods for the Stokes problem does not exist for certain elements. In particular, we have shown that enriching Q4 and B8 elements with standard bubble functions produces unstable results. Clearly, this work highlights the need for more emphasis in the development of bubble function enriched methods and the exact nature of their relationship to stabilized formulations. . The Kronecker product of these matrices is an np × mq matrix, and is defined as. • The divergence of the jacobian matrix. Consider the jacobian matrix J := with a simple identity, we can derive the divergence of the jacobian matrix as follows. To further clarify, for a Q4 element,x, DN , and D 2 N are defined aŝ. . . .. • The Laplacian of a bubble function. Noting that β is a constant vector and making use of th divergence of the jacobian matrix as shown above, the Laplacian of a bubble function can be computed as follows. . . . pressure for 36 TET4 elements using the enriched formulation.

O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


Computational performance of aggregated distillation models Compartmental and aggregated modeling is used to derive low-order (reduced) dynamic models from detailed models of staged processes. In this study, the aggregated modeling method of [Lévine, J., & Rouchon, P. (1991) . Quality control of binary distillation columns via nonlinear aggregated models. Automatica, 27, 463] is revised with the objective of deriving computationally efficient models for real-time control and optimization applications. A simple implementation of the original method not requiring the specification of compartments is presented. The resulting DAE models are converted into ODE models by pre-solving and substituting the algebraic equations resulting from the reduction procedure, which is the key step to increase simulation speed. To study this, the performances of several full and reduced distillation models, with and without base-layer controllers, are compared using different numerical integrators. It is found that while the reduced DAE models are computationally not advantageous, the reduced ODE models decrease the simulation time by a factor of 5-10. With the establishment of dynamic real-time optimization and model predictive control as state-of-the-art methods to efficiently operate industrial processes, reduced models with low computational complexity are in the focus of current research (Allgöwer & Zheng, 2000; Marquardt, 2001; van den Berg, 2005) . In particular, reduced nonlinear physically based models are of high interest for the prediction of the system behavior over a wide range of operating conditions. Many model reduction techniques have been developed for nonlinear systems (Marquardt, 2001; van den Berg, 2005) , most of which produce models of lower order. This, however, does not guarantee that the reduced models show a computationally better performance than the original models they were derived from (van den Berg, 2005) . This is because a reduced model is most likely less accurate than the original full model, and because the numerical complexity of the full model is often retained in the equations of the reduced model.. For nonlinear model reduction of distillation columns, several model reduction and simplification methods have been developed in the past (Benallou, Seborg, & Mellichamp, 1986; Cho & Joseph, 1983; Khowinij, Bian, Henson, Belanger, & Megan, 2004; Kienle, 2000; Kumar & Daoutidis, 2003; Lévine & Rouchon, 1991; Marquardt, 1990; Skogestad, 1997) . Among these are the method of compartmental modeling (Benallou et al., 1986) and later the improved variant of aggregated modeling by Lévine and Rouchon (1991) . The latter method is used for deriving the reduced models investigated in this study. It is based on partitioning a distillation column into "compartments" consisting of "steady-state" trays and dynamic "aggregation" trays, and using a singular perturbation argument (Kokotovic, Khalil, & O'Reilly, 1986) to derive a reduced-order model. Among its advantages is the perfect steady-state agreement with the original model, a simple derivation, and good control of the reduced model complexity.. Originally, these methods were intended for nonlinear controller design, for which a low-order model is necessary. More recently, they have been used to reduce the simulation time in real-time applications (Bian, Khowinij, Henson, Belanger, & Megan, 2005; Khowinij et al., 2004 Khowinij et al., , 2005 . However, it is shown in this study that while only transforming the original system into a reduced system in differential-algebraic equation (DAE) form does not improve the simulation speed of the reduced model, a subsequent elimination of the algebraic equations is necessary to obtain a reduced model in ordinary differential equation (ODE) form, which shows a significantly improved computational performance compared to the original model. On a more fundamental level, it is shown that the notion of compartments is not necessary in the derivation of the reduction method. This greatly simplifies the derivation and makes the extension of the method to more complex systems straightforward.. The paper is organized as follows: In Section 2, the full model for a binary distillation column, and the derivation of reduced models from this using aggregated modeling is described. Important implementation details and properties of the models are given. In Section 3, the framework for testing the computational performance of the models is explained, discussing the input signal, the model parameters and the numerical solvers used for simulating the models. The results of the simulations are given in Section 4. Section 5 discusses the results of the simulations, and details and possible extensions of the reduction method. A summary and conclusions are given in Section 6. In this study, the tray aggregation method of Lévine and Rouchon (1991) has been used to derive reduced models of a binary distillation column model. It has been shown that the original derivation, which partitions the column into "compartments" of consecutive trays, can be simplified to a procedure which only requires the specification of aggregation trays and is independent of the choice of compartment boundaries. This gives the resulting reduced model a favorable numerical structure and makes the extension to more complex models straightforward. The original method yields a DAE model with the same number of variables as the original model. Because of the banded Jacobian structure of the reduced model, the algebraic equations of the DAE models can be eliminated from the model by off-line solution and substitution of the tabulated solution values as functions of the dynamic variables into the dynamic equations, yielding low-order ODE models. The numerical performance of these models has been assessed by simulations using four different numerical integrators. While simulation of the DAE models showed no gain in simulation speed, the reduced models yielded an improvement of up to factor 10. Due to the reduced stiffness of the models, a non-stiff integrator can be used for integration. The inclusion of a controller in the bottom section of the column has been investigated. While the application of a PI-controller to the reduced model is easily possible, the controller can also be directly incorporated into the reduced model assuming perfect control. Both variants show good performance, decreasing simulation time about six times.. The computational gains that can be achieved by the reduced models form make these kind of models attractive for use in real-time optimization applications. In more complex models, the performance of the reduced models will depend on the complexity of the right hand sides as well as the number of independent variables for the tabulation of the steady-state tray solutions.

B I O O B O O O B I O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O B O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


The use of discrete orthogonal projections in boundary element methods In recent papers by Sloan and Wendland (1999) , Grigorie and Sloan (1998) and Grigorie , Sloan and Brandts (2000), a formalism was developed that serves many important and interesting applications in boundary element methods: the \commutator property" for splines. Based on superapproximation results, this property is, for example, a tool of central importance in stability a n d convergence proofs for qualocation methods for boundary integral equations with variable coe cients.Another application is the transfer of superconvergence properties from constant-coe cient boundary integral equations to the variable coe cient case. The heart of the theory is formed by the concept \discrete orthogonal projection", that arises when the L 2 -orthogonal inner product is discretized by possibly non-standard quadrature rules.In this paper, we present a n o verview of the theory of discrete orthogonal projections, and a new set of numerical experiments that con rm the theory. The main conclusion is that the presence of variable coe cients of a certain smoothness does not in uence superconvergence in a negative w ay, and that henceforth the use of superconvergence-based a posteriori error estimators in this particular case is theoretically justi ed. This paper aims to summarize recent results in the area of discretization methods for boundary integral equations. Those results were obtained by the use of a theory that involves the concept of so-called discrete orthogonal projections. As we will show, discrete orthogonal projections provide a connecting framework between the left-bank of collocation methods and the right-bank of Galerkin boundary element discretizations. We will, however, mainly concentrate on the massive r i v er of qualocation methods, which is situated in between.

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Models and temporal logical specifications for timed component connectors Abstract Component-based software engineering advocates construction of software systems through composition of coordinated autonomous components. Significant benefits of this approach include software reuse, simpler and faster construction, enhanced reliability, and dramatic reductions in the complexity of construction of provably correct critical systems, many of which involve real-time concerns. Effective, flexible component composition by itself still poses a challenge today and yet the special nature of real-time constraints makes component-based construction of real-time systems even more demanding. The coordination language Reo supports compositional system construction through connectors that exogenously coordinate the interactions among the constituent components which unawarely comprise a complex system, into a coherent collaboration. The simple, yet surprisingly rich, calculus of channel composition that underlies Reo offers a flexible framework for compositional The task of designing a complex concurrent system with several components requires a coordination model that formalizes their mutual interactions. The internals of black-box components cannot be modified to implement such coordinated interactions. Coordination, therefore, becomes the responsibility of the "glue-code" that interconnects the constituent components of a composite system, and of its underlying run-time middle-ware. Reo [6] offers a powerful glue language for implementation of coordinating component connectors based on a calculus of mobile channels.. In this paper, we consider the real-time aspects of Reo when the behavior specification of channels and component interfaces can involve timing constraints. Because connectors, not components, are the primary concern in Reo, our primary interest here is with channels whose behavior involves temporal constraints; and with their composition. For instance, a deadline t for the availability of some data can be formalized as the behavior of a FIFO channel that associates an expiration date, t, with every data item that enters its buffer: the channel loses a data item in its buffer t units of time after it enters through its source (unless, of course, it is dispensed through its sink in the meanwhile). Another example is a timer channel that becomes activated by a data item through its source, after which it returns a timeout signal through its sink, after a specified delay of exactly t units of time.. As the operational model for Reo connector circuits, we use timed constraint automata (TCA) which extend their untimed version [9] with the concepts borrowed from classical timed automata with location invariants [2, 16] . TCA have two kinds of transitions: (1) internal changes of the locations caused by some time constraints and (2) transitions that represent the synchronized execution of I/O-operations at some of the ports. Using ideas similar to [9] , the construction of a timed constraint automaton from a given timed Reo circuit can be performed in a compositional manner, using composition operators on TCA that model Reo's operators join and hide to build complex connectors out of instances of basic channel types.. One conceptual difference between TCA and classical timed automata is the treatment of immediate actions or urgent synchronous channels, as they are used, e.g., in the tools [20, 17, 37] . The assumption that synchronous I/O-operations must be executed as soon as they become enabled makes no sense in our framework. For instance, assume that we have a FIFO channel carrying data from node A to node B and a synchronous channel from B to another node C. As soon as A places a value in the FIFO buffer it becomes available for consumption through node B, and thus, the synchronous communication between B and C becomes enabled. On the other hand, the input and output of the same data item must not occur simultaneously through a FIFO channel, by its definition. Thus, we need a delay for the synchronization between B and C. Moreover, Reo allows to explicitly specify deadlines of "shortly delayed" activities or other time constraints (e.g., lower bounds for the delay) using an appropriate combination of timed channels.. The semantics of the TCA and timed Reo circuits relies on timed data streams as in [7, 9] , comprising a formalization of the possible data-flow at each node over time. To specify a desired coordination mechanism, we use a variant of linear temporal logic (LTL) [22, 27] with real-time constraints, which we call timed scheduleddata-stream logic (TSDSL) and has a semantics based on timed data streams. TSDSL essentially relies on a combination of the time-abstract temporal modalities in LTL and timed regular expressions [10] . We show through a series of examples how TSDSL can serve as a specification formalism for (timed) Reo circuits, sketch the ideas of a model checking algorithm, and explain the relation of TSDSL with refinement relations.. Related models. There are several other related realtime models that also focus on aspects of coordination. Timed interface automata (TIA) [1] or real-time variants of I/O-automata, e.g., [13, 19, 24] , are related to TCA in the same way as their untimed versions. I/Oautomata rely on the assumption of input-enabledness which is not required (and would not make sense) in constraint automata.. The purpose of TIA is orthogonal to our approach involving timed Reo connectors and TCA. (There are some conceptional differences, e.g., TIA use action labels rather than port names, but these are not important as the formal definition of TIA and TCA can be adapted to eliminate these differences.) The major goal of TIA is to provide a formalism to specify and to check the compatibility of real-time components by means of their interfaces. Our focus is on compositional reasoning about (design and analysis of) channel-based coordination mechanisms, based on their data-flow. Thus, our framework allows to design and analyze a coordination context in which certain components are used and to construct their interfaces, while the approach of interface automata allows to check a-posteriori whether a design makes the components work together in the desired way.. Although compositionality in timed Reo and TCA is in the spirit of real-time process algebras, e.g., [21, 29, 36 ], Reo's philosophy of composing connectors out of a variety of basic channel types via join and hiding and supporting any kind of synchronous or asynchronous communication differs from classical process algebra approaches which provide operators for modeling choice, parallelism, and recursion (all of which are implicit in Reo).. In some respects, Reo circuits superficially resemble Petri nets. However, there are major differences between the two. Petri nets are constructed out of a fixed set of building blocks (i.e., places, transitions, and arcs), each with a fixed behavior, that can be composed in a prescribed fashion. In contrast, Reo defines a fixed set of composition rules and allows an arbitrary set of user defined channels as primitives with arbitrary behavior, on which its composition rules can be applied to construct connector circuits. This allows a harmonious combinations of synchrony and asynchrony in the same model which is not possible in Petri nets. It also allows incorporation of arbitrary computational entities into a composed Reo circuit. Specifically, as we show in this paper, real-time constraints can be easily incorporated into Reo simply by adding a few channels with time-sensitive behavior to the user-defined repertoire of primitives used in the construction of circuits, without any extension or revision of the Reo model or its composition rules. On the other hand, to express temporal constraints in Petri nets, various extended models have been proposed and studied, each revising the semantics of a basic Petri net model by associating temporal constraints with (1) the availability of tokens in places, (2) transitions, or (3) arcs [18, 23, 28, 31] .. Using proper time-sensitive channles, Reo can cover the temporal constraints modeled in various timed Petri nets. Timed or un-tiemd Petri nets differ from Reo in that synchrony and exclusion constraints propagate through (the synchronous sub-sections of) Reo circuits. This is generally not the case in Petri nets, because their transitions are local. Petri net transition nodes enable them to directly synchronize otherwise unrelated events, thus enforcing a synchronous and of several arcs/events. However, Petri nets have no primitive for the dual synchronous or of several arcs. The or of several arcs is possible only if they end in the same place, which implies the commitment of moving a token into that place. This means that events/arcs can be directly andsynchronized to compose more complex synchronous transitions (i.e., one-step atomic transactions), but a synchronous or of events/arcs is not possible, i.e., two transitions cannot be connected together without an intervening place/commitment. This disallows a direct modeling of composite atomic transactions in Petri nets and prevents arbitrary combinations of synchrony and asynchrony.. Organization of the paper. Timed constraint automata are introduced in Sect. 2. Section 3 contains a brief overview of Reo. In Sect. 4 we introduce timed primitive channels for constructing Reo circuits, provide some examples for Reo circuits with timing constraints, and explain how timed constraint automata can serve as their operational model. Timed scheduled-data-stream logic (TSDSL) is introduced in Sect. 5. In addition, we provide some examples to illustrate how TSDSL can serve to specify timed component connectors and sketch the main steps of a TSDSL model checking algorithm. Sect. 6 concludes the paper. In this paper, we introduced a formal model to reason about timing constraints for Reo component connectors. We presented composition operators for join and hide that can serve as a basis for the automated construction of an automaton-model from a given (timed) Reo circuit, and as a starting point for its formal verification. Particularly, (slightly modified versions of) well-known algorithms for checking time-lock freedom in ordinary timed automata can serve for checking the realizability of the coordination mechanisms of a Reo circuit with timing constraints. Moreover, we suggested a linear-time temporal logic for reasoning about the real-time behavior of component connectors based on their timed scheduled-data streams. Finally, we sketched how the standard model checking algorithms for timed automata can be adapted for our setting.. Our future work includes an implementation of the presented model checking algorithms and case studies. Moreover, we intend to study an alternating-time logic in the style of [4] that allows to reason about the possibility for certain components to cooperate such that a given (real-time) property holds.

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A Tool and Methodology for AC-Stability Analysis of Continuous-Time Closed-Loop Systems Index Terms-AC stability, small-signal circuit stability, frequency instability, closed loop system stability. LTHOUGH small-signal stability of analog and mixedmode signal integrated circuits is a fairly old problem and has been studied in many ways both by circuit theory and in every-day practice, it is still a significant source of problems that may render a circuit non-operational under certain conditions. What is presented in this paper is a M. M. Milev is with High Performance Analog division, High Speed business unit at Texas Instruments Inc., Tucson, AZ 85749 USA (e-mail: milev_momtchil@ti.com).. Rod Burt is with High Performance Analog division, Precision Linear Products at Texas Instruments Inc., Tucson, AZ 85749 USA (e-mail: burt_rod@ti.com).. method [2] and a tool that allow small-signal circuit ACstability to be evaluated for a continuous-time closed-loop systems without breaking the loop. This is especially useful where breaking the loop is very hard or impossible without affecting circuit's performance or biasing conditions. Moreover, if the methodology is employed by an automated design analysis tool, it can evaluate the stability not only of main-loop effects but also of local loops often present in current mirrors, bias circuits, emitter followers and other circuits that otherwise could go undetected and untested. Such a tool could allow for automatic loop identification and fullcircuit stability analysis, which gives better picture of the circuit's sensitive nodes/loops as opposed to black-box phasemargin AC-analysis. In this way, this method offers several advantages over the traditional methods of evaluating smallsignal circuit stability as node pulsing during transient analysis and Bode/phase-margin-plots in AC-analysis.

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Location, Localization, and Localizability Location-aware technology spawns numerous unforeseen pervasive applications in a wide range of living, production, commence, and public services. This article provides an overview of the location, localization, and localizability issues of wireless ad-hoc and sensor networks. Making data geographically meaningful, location information is essential for many applications, and it deeply aids a number of network functions, such as network routing, topology control, coverage, boundary detection, clustering, etc. We investigate a large body of existing localization approaches with focuses on error control and network localizability, the two rising aspects that attract significant research interests in recent years. Error control aims to alleviate the negative impact of noisy ranging measurement and the error accumulation effect during cooperative localization process. Network localizability provides theoretical analysis on the performance of localization approaches, providing guidance on network configuration and adjustment. We emphasize the basic principles of localization to understand the state-of-the-art and to address directions of future research in the new and largely open areas of location-aware technologies.Keywords location-based services (LBS), localization, error control, localizability, wireless ad-hoc and sensor networksThe proliferation of wireless and mobile devices has fostered the demand for context-aware applications, in which location is viewed as one of the most significant contexts. For example, pervasive medical care is designed to accurately record and manage patient movements [1] [2] ; smart space enables the interaction between physical space and human activities [3] [4] ; modern logistics has major concerns on goods transportation, inventory, and warehousing [5] [6] ; environmental monitoring networks sense air, water, and soil quality and detect the source of pollutants in real time [7] [8] [9] [10] [11] ; and mobile peer-to-peer computing encourages content sharing and contributing among mobile hosts in the vicinity [12] [13] . In brief, location-based service (LBS) is a key enabling technology of these applications and widely exists in nowadays wireless communication networks from the short-range Bluetooth to the long-range telecommunication networks, as illustrated in Fig.1 .Recent technological advances have enabled the development of low-cost, low-power, and multifunctional sensor devices. These nodes are autonomous devices with integrated sensing, processing, and communication capabilities. With the rapid development of wireless sensor networks (WSNs), location information becomes critically essential and indispensable. The overwhelming reason is that WSNs are fundamentally intended to provide information on spatial-temporal characteristics of the physical world; hence, it is important to associate sensed data with locations, making data geographically meaningful. For example, a number of applications, such as object tracking and environment monitoring, inherently rely on location information. A detailed survey on location-based applications can be found in [14] [15] .Location information also supports many fundamental network services, including network routing, topology control, coverage, boundary detection, clustering, etc. We give a brief overview as follows. Location-awareness is a key feature of futuregeneration networks, enabling a large number of pervasive applications. In this article, we have provided an overview of existing localization approaches and discussed several research challenges, including locationaided network services, geographical information measuring, and design principles of algorithms. We put emphasis on error control mechanism and localizability theory, two rising aspects that attract significant research interests in recent years. We offer this survey to help researchers to understand the state-of-the-art and to address directions of future research in the new and largely open areas of location-aware technologies.

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Limits of a conjecture on a leakage-resilient cryptosystem Recently it was conjectured that an ElGamal-based public-key encryption scheme with stateful decryption resists lunch-time chosen ciphertext and leakage attacks in the only computation leaks information model.We give a non-trivial upper bound on the amount of leakage tolerated by this conjecture. More precisely, we prove that the conjecture does not hold if more than a Leakage-resilient cryptography [1, 2] is a recent research line that aims at building countermeasures and/or defences against side-channel attacks while providing security reductions in a provable security manner. The methodology is as follows: an abstract model specifying the leakage data is chosen and the goal is to exhibit a reduction from a hardness assumption to a hypothetical side-channel adversary. The theory of leakageresilient cryptography has witnessed a tremendous activity despite its short life. However, meeting the strongest security levels (resiliency against continual leakage attacks [3] ) under the weakest assumptions (memory leakage [3] /auxiliary input [4] ) is still out of reach from a practical point of view. To our knowledge existing schemes are inecient when compared to their counterparts in the non-leakage setting; moreover, current leakage-resilient constructions are conceptually far more complex than those a practitioner currently nds in its cryptographic tool-box.. In this sense it is worth to mention the work by Kiltz and Pietrzak [5] . They propose BEG a pairingbased analogue of the ElGamal encryption scheme [6] with stateful decryption which is leakage-resilient against lunch-time chosen ciphertext and leakage attacks (CCLA1). The latter means that the classical distinguishing adversary against ElGamal is given access to decryption and leakage oracles only before the challenge ciphertext is given. The basic idea is to set the ElGamal secret key to be a group element (in contrast to an integer), and then multiplicatively share it. While splitting the secret key before decryption is a well-known technique, the novelty of this work is to propose to split a group element rather than an integer. It is shown that if the secret key length is κ, then the BEG scheme is secure against leakage of at most λ κ 2 bits at every decryption step. More precisely, λ < κ 2 − ω (log κ) to make it infeasible to guess the remaining bits of the secret key by a brute force attack. Their proof uses the so-called Generic Bilinear Group Model [7] .. The authors of [5] discuss the limitations of getting a security proof for a similar leakage-resilient property of ElGamal with stateful decryption over arbitrary groups. Nevertheless they conjecture that, for certain arbitrary groups where the Decisional Die-Hellman problem is hard, ElGamal with stateful decryption, that they call EG , might be resistant against side-channel attacks that abide by the Continual Leakage Split-State model.. Our Contribution In this work we impose a limit on the conjecture from [5] , by proving that if a minimum of 3 8 + o (1) κ bits are leaked at every invocation of the secret key, a CCLA1 attack exists against ElGamal with stateful decryption scheme EG that recovers the secret key. Interestingly, our limit to the conjecture applies to any arbitrary instantiation of the underlying group. To achieve this result we dene a new problem, called Hidden Shares -Hidden Number Problem, which is a close but new variant of the Hidden Number Problem [8] .. Open Problem As far as we know, no (stateful) ElGamal-based public-key encryption scheme with constant public-key size exists in the literature oering (provable) resistance against continual leakage attacks (in the standard model). Finding such a scheme remains a challenging open question.

O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


Emergent ad hoc sensor network connectivity in large-scale disaster zones We introduce a disaster-zone-monitoring web-based application. While using this application, the user may simulate different large-scale disaster zones. He may use tools to define a disaster zone and its communication requirements. The web application uses the Google Earth infrastructure and is publicly available to use online during the conference from every computer connected to the Internet. The evolving deployment of nodes will be updated each second to reflect the current state of the entities residing within the monitored zone.The user will be able to navigate through the disaster zone to inspect the dynamically changed environment, and to learn about node deployment and the current network connectivity and service availability. He could ask the system to find the number of agents required to be deployed and present this deployment. The user also will be able to define the budget limitations. Thus, the system will derive the number of agents, their deployment, and the resulting system utility. Given a system utility, the user can decide whether to adopt the deployment even though it does not guarantee full coverage, or to increase the budget to improve system utility.In a large-scale disaster such as an earthquake or a flood, one of the first things to collapse is the communication infrastructure. Communication is an essential means for rescue operations, and survivability of victims of such disasters decreases sharply with every minute that passes. Therefore, rapidly reviving the communication infrastructure in a large-scale disaster zone is crucial to saving many lives.Nodes of an ad hoc sensor network should support both 1 This demonstration is a live demo software.Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. local and global requirements. The local requirement is to allow nearby users of mobile phones, computers, sensors, and PDAs to receive service, while the global requirement is to maintain network connectivity. Agencies responsible for establishing such networks wish to balance between the need to service as many users as possible and the maintenance of network connectivity. Formally, this balance could be defined by the agencies as a utility function of the system. These agencies wish to maximize the utility of the system under the limitation of a given budget. For the purpose of this work we narrow the budget considerations to be the number of network nodes. We define the system utility as the percentage of successfully delivering a message between two randomly chosen users. The utility is measured by averaging over M sets of randomly chosen users while M >> number of users.Reflecting recent technology advances, we propose to use thousands of small, short-range, inaccurate, low-cost, mobile nodes to support the requirements. Following the fractal behavior of the network we show a phase transition in the utility of the system as a function of the number of nodes. That is, (i) for a few nodes, there is no applicable deployment while (ii) for many nodes any random deployment achieves the maximum utility, and (iii) the transition between zero utility and maximum utility is sharp.Considering the phase transition phenomenon, we show how to determine the number of agents needed to maintain such ad hoc sensor networks and demonstrate an algorithm to drastically reduce the number of nodes required for the phase transition. We propose to apply intelligent behavior to every node. This behavior considers very limited partial information obtained by the node. To reduce resource consumption, a node does not use communication with other nodes for implicit cooperation but only for acquiring the location of its neighboring nodes.Our model relies on the percolation theory [1], specifically on the site-percolation model. According to the percolation model a geometrical construction of sites and bonds between them is referred to as a lattice. A lattice may be considered a graph of vertices and edges, respectively. An edge may exist only between two sites considered as closest neighbors; that is, the distance between them is smaller than a predefined range. The percolation model may be characterized as two types, the bond and the site. In a bond percolation model a probability p represents the probability for an edge to be 1377 978-81-904262-7-5 (RPS) c 2007 IFAAMAS

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Efficient Context-Sensitive Plausible Inference for Information Disclosure Plausible inference is an essential aspect of logic-based information disclosure. This paper proposes a context-sensitive plausible inference mechanism based on a so-called index expression belief network. Plausible inference is cloaked as probabilistic evidence propagation within this network. Preliminary experiments show general evidence propagation algorithms to be too ine cient for real-life information disclosure applications. The paper sketches two optimizations whereby e cient, special-purpose evidence propagation may be realized. The logic-based approach to the disclosure of information has been around for some time now, Van Rijsbergen, 1986; Van Rijsbergen, 1989] . In this approach, an information object is deemed relevant with respect to a searcher's request if this request can be proven from the characterization of the object by employing a set of rules of inference. The inference mechanism used is crucial to the e ciency and e ectiveness of the disclosure. As requests tend to be only vague representations of a searcher's information need and the characterizations of information objects are typically incomplete, being able to e ectively reason with uncertainty is a fundamental to any inference mechanism used for information disclosure. The theme of this paper is the elaboration of a plausible inference mechanism.. For the purpose of e ective plausible information disclosure, applying context-free rules of inference is shown to be insu cient: these rules tend to disregard vital parts of the context provided by initial object characterizations thereby resulting in imprecise information disclosure. In contrast, the plausible inference mechanism proposed here drives context-sensitive inference. It is founded on a probabilistic belief network, representing all variables involved in the problem of information disclosure and their probabilistic interdependencies. Such a network allows for e cient computation of probabilities of relevance for information objects, taking probabilistic interdependencies into account. In this framework, information disclosure is modelled by computing updated probabilities of relevance with respect to a given request.. The paper is organized as follows. Section 2 introduces the language of index expressions for describing the contents of information objects and provides some further background to logicbased information disclosure; an important issue mentioned is the inadequacy of context-free plausible inference. Section 3 introduces the index expression belief network and the associated context-sensitive plausible inference mechanism. Section 4 shows how this inference mechanism may be employed in real-life information disclosure applications and reports on some preliminary experiments recently performed using the Cran eld document collection. Section 5 addresses the feasibility of the inference mechanism and discusses an optimization taking advantage of the characteristics of the index expression belief network. The paper is rounded o with some conclusions and directions for further research. In this paper, a context-sensitive plausible inference mechanism for information disclosure has been proposed, based on the index expression belief network. The results obtained from the preliminary experiments with this inference mechanism are encouraging. These experiments, however, are too small-scaled to provide real insight into the potential e ectiveness of our approach; we hope to report on larger experiments in the near future. The feasibility of the belief network approach for driving plausible inference in information disclosure remains an area of continuing interest.

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