Performability evaluation of emergency call center

Emergency call centers serve people in utmost circumstances; hence they should be highly dependable. Availability and performance are key aspects in call centers. Architectural models, service policies, and redundancies are attributes for defining and evaluating the overall operation of such systems. In this work, we performed the performability evaluation of an important emergency call center located in a large city in Brazil. The results showed that the system’s downtime is considered high, so, we proposed a new architecture to improve the system’s performability. The results obtained in this paper can be used to provide support for decisions on interventions in the emergency call center to improve its performability. It is expected that the models presented in this paper will be useful in a variety of emergency call centers.     

Statistical properties of controlled fluid flows with applications to control of mixing

In this paper, we study statistical properties of fluid flows that are actively controlled. Statistical properties such as Lagrangian and Eulerian time-averages are important flow quantities in fluid flows, particularly during mixing processes. Due to the assumption of incompressibility, the transformations in the state space can be described by a sequence of measure preserving transformations on a measure space. The classical Birkhoff's pointwise ergodic theorem does not necessarily apply in the context of sequences of transformations. We call B-regular a sequence for which this theorem holds. Motivated by mixing control concepts, we define three notions of asymptotic equivalence for sequences of transformations. We show an example in which Birkhoff's pointwise ergodic theorem does not hold even when a ‘strong’ asymptotic equivalence to a B-regular sequence is assumed. Under a ‘very strong’ asymptotic equivalence condition, we prove B-regularity. In the context of optimize-then-stabilize strategy for mixing control, we also prove that very strong asymptotic equivalence to a mixing sequence implies mixing. The mean ergodic theorem and the Poincare’ recurrence theorem are also proven for sequences of transformations under suitable asymptotic equivalence assumptions.     

Assessing the ‘insider–outsider threat’ duality in the context of the development of public–private partnerships delivering ‘choice’ in healthcare services: A sociomaterial critique

Containing the ‘outsider’ threat to the information systems of organisations as well as recognising the disruptive potential of ‘insiders’ are fundamentals of security management. However, the recent development of public–private partnerships in the UK requires a reassessment of the continuing utility of such dualities. This paper draws upon a sociological understanding of the complexities of organisational practices as well as a grounded case study of the implementation of the NHS ‘Choose and book’ service across both public and private healthcare organisations in order to challenge these essentialist forms of sociotechnical analysis. The paper proposes a sociomaterial understanding of information systems and organisational dynamics that does not seek to separate out distinct ‘human’ and ‘technical’ information security risks. Rather, it asserts that the organisational outcomes of the introduction of new information systems are necessarily emergent and contingent, and it is with these indeterminate realities that security analysts have to engage.     

The stuttering principle revisited

It is known that LTL formulae without the ‘next’ operator are invariant under the so-called stutter equivalence of words. In this paper we extend this principle to general LTL formulae with given nesting depths of both ‘next’ and ‘until’ operators. This allows us to prove the semantical strictness of three natural hierarchies of LTL formulae, which are parametrized either by the nesting depth of just one of the two operators, or by both of them. Further, we provide an effective characterization of languages definable by LTL formulae with a bounded nesting depth of the ‘next’ operator.This paper is a revised and extended version of [6].     

Queueing analysis and optimal control of and systems

We first consider a finite-buffer single server queue where arrivals occur according to batch Markovian arrival process (BMAP). The server serves customers in batches of maximum size ‘b’ with a minimum threshold size ‘a’. The service time of each batch follows general distribution independent of each other as well as the arrival process. We obtain queue length distributions at various epochs such as, pre-arrival, arbitrary, departure, etc. Some important performance measures, like mean queue length, mean waiting time, probability of blocking, etc. have been obtained. Total expected cost function per unit time is also derived to determine the optimal value N^* of N at a minimum cost for given values of a and b. Secondly, we consider a finite-buffer single server queue where arrivals occur according to BMAP and service process in this case follows a non-renewal one, namely, Markovian service process (MSP). Server serves customers according to general bulk service rule as described above. We derive queue length distributions and important performance measures as above. Such queueing systems find applications in the performance analysis of communication, manufacturing and transportation systems.     

A framework for balanced service and cross-selling by using queuing science

Contact centers are complex call centers to handle large volume of inbound, outbound or both types of calls depending on the business purpose. Call centers assume the role of the primary contact medium for many companies from a wide range of industries with their customers or clients. Despite of being seen traditionally as adding cost to the companies’ bottom lines, call centers are now viewed by many companies to turn a service request into an opportunity to sell additional products and services. This sales attempt is called cross-selling. The opportunity to generate profit from an existing customer-base is a key factor for a successful call center. This paper introduces a framework for balancing cross-selling and service activities in a call center setting from a queuing science point of view. The main goal of this study is to introduce a framework to maximize a call center’s performance without degrading the service quality. Our framework is based on the usage of real-time queue characteristics, customer profile information and server-skill set information from a cross-sell point of view.     

Discovering timely information in MANETs

Timely information refers to information whose ‘most recent’ or ‘latest’ instance is most valuable. In mobile ad hoc networks (MANETs), multiple instances of a piece of timely information may be produced by different nodes at different points in time. The problem is to discover the ‘latest’ instance among all existing instances. Within the context of MANETs, timely information discovery is fundamentally different from the existing resource/service discovery problem whose goal is to discover either any instance or a subset of instances which satisfy a local query constraint that can be specified and evaluated using only local attributes of each individual node. In contrast, the timely information discovery problem imposes the global (timeliness) constraint which should best be evaluated when all the instances are considered to determine the latest instance. The complication of discovering timely information arises from the existence of multiple instances of the information, which are produced at different points in time by different nodes in the network, and the need to collect all these instances to decide the latest instance. For MANETs, the lack of infrastructure supports, frequent topology changes, and potential packet loss in wireless communications further challenge the problem of timely information discovery. This paper describes a self-organizing, peer-to-peer based approach, termed ALADIN, to discovering timely information in MANETs. In ALADIN, nodes that produce instances of the timely information are peers who self-organize an adaptive and distributed ‘search infrastructure’ to facilitate the discovery of the latest instance. A simulation study shows that ALADIN is scalable without incurring network-wide flooding in the case of large-scale networks and popular timely information, and yields a high chance of discovering the latest instance in the presence of mobility.     

Moving with the Times: IT Research and the Boundaries of CSCW

The field of CSCW research emerged with the development of distributed computing systems and attempts to understand the socially organized (‘collaborative’ or ‘cooperative’) nature of work in order to embed such systems in the workplace. As a field of interdisciplinary inquiry CSCW was motivated by technological developments and the need to understand the particular contexts within which those developments were intended to resonate. In other words, it is no mere accident that CSCW took work as its topic and resource – the historical nature of IT research from which the field emerged meant that for all practical purposes it could not be otherwise. Yet times change. IT research moves on. Today mobile, ambient, pervasive, ubiquitous, mixed reality and wearable computing, et cetera, are of fundamental concern to the contemporary computing research community. Furthermore, these developments are accompanied by a movement away from the workplace to focus on diverse settings in everyday life: homes, games, museums, photography, tourism, performances, indeed diverse bodies of people and pursuits that generally fall under the conceptual rubric of the ‘ludic’. Accompanying this shift away from work is a call for new approaches and concepts that will enable researchers to better understand the ludic and inform design appropriately. In this paper we seek to address the boundaries of CSCW and the ability of CSCW to respond to contemporary research agendas. We present an ethnomethodological study of a location-based mixed reality game to demonstrate the continued relevance of CSCW approaches and concepts to contemporary agendas in IT research.     

Some applications of an Implicit Duality Theorem to connections of structures of special types including Dirac and reciprocal structures

In this paper, we present some applications of an Implicit Duality Theorem which was originally a folklore result on Ideal Transformers in Electrical Network Theory. We show, among other things, that results on reciprocal networks (due to Tellegen (Proc. Inst. Radio Engrs. 14 (1953) 265), and Dirac Structures (due to van der Schaft (in: J.W. Polderman, H.L. Trentelman (Eds.), From Intelligent Control to Behavioural Systems. University of Groningen Press) follow as a consequence. These results have the form ‘interconnection of structures of a particular kind yields a structure of the same kind’. Also discussed is the question ‘given smaller structures of a given kind and a desired structure of the same kind, can the former be interconnected to yield the latter?’. We also indicate the range of possible generalizations of this result.     

Practical optimization by OR and simulation

This paper aims to promote and illustrate that the combination of classical operations research (queueing, linear and stochastic dynamic programming) and simulation (techniques and tools) can be most beneficial.First, an instructive example of parallel queues will be studied to address the question whether these queues should be pooled or not. This simple example already shows the necessary and fruitful combination of queueing and simulation. Next, the combined approach will be applied to and illustrated for:

• pooling (or not) of call centers,

• pooling (or not) in hospitals,

• checking-in at airports,

• flight catering, and

• assembly lines.

The applications show that “to pool or not” is not the only question for which further research and application of a combined OR-Simulation approach can be most fruitful for ‘practical optimization’.     

Interpreting SWRL Rules in RDF Graphs

An unresolved issue in SWRL (the Semantic Web Rule Language) is whether the intended semantics of its RDF representation can be described as an extension of the W3C RDF semantics. In this paper we propose to make the model-theoretic semantics of SWRL compatible with RDF by interpreting SWRL rules in RDF graphs. For dealing with SWRL/RDF rules, we regard ‘Implies’ as an OWL class, and extract all ‘Implies’ rules from an RDF database that represents a SWRL knowledge base. Each ‘Implies’ rule is grounded through mappings built into the semantic conditions of the model theory. Based on the fixpoint semantics, a bottom-up strategy is employed to compute the least Herbrand models.     

Stability conditions for a class of time-varying discrete-time systems

This paper deals with the stability conditions for a class of dynamical discrete-time systems, called ‘P-invariants’ and ‘not P-invariants’. Stability conditions are given in terms of polyhedral convex cones and are obtained by using some extensions on M-matrices.     

The role of student learning styles, gender, attitudes and perceptions on information and communication technology assisted learning

The present study adopts an illuminative approach to evaluate students’ initial attitudes towards the use of information and communication technology (ICT). Ninety-nine undergraduate science students participated in this study and their learning styles were classified according to Honey and Mumford (1986) (Honey, P., Mumford, A., 1986. The Manual of Learning styles. Peter Honey, 10 Linden Avenue, Maidenhead) learning style questionnaire. Student learning styles were classified as activist, reflector, theorist, or pragmatist. No significant difference in learning styles was observed between genders and between student cohorts. Six dimensions to student attitudes toward ICT were identified as follows; ‘comfort’, ‘interactivity’, ‘self-satisfaction’, ‘value new technology’, ‘experience’ and ‘context’. Students exhibited low scores in the attitude dimensions of ‘value new technology’, ‘interactivity’ and ‘context’ indicating that they were uncomfortable with computers, were unhappy about the lack of personal contact and would prefer to learn in a more traditional mode. A significant, though weak, negative correlation between the ‘theorist’ and the ‘interactivity’ and ‘context’ attitude dimensions was also observed. In addition, based on the results of this study it appears that first year students exhibit a more positive perception of ICT supported learning than second and third year students. Though the use of ICT in higher education is becoming more widespread based on the results of this study student use of the technology may be limited by a negative attitude toward a style of teaching which is not consistent with their past learning experiences.     

Estimation of model quality

This paper provides an introduction to recent work on the problem of quantifying errors in the estimation of models for dynamic systems. This is a very large field. We therefore concentrate on approaches that have been motivated by the need for reliable models for control system design. This will involve a discussion of efforts that go under the titles of ‘estimation in ’, ‘worst-case estimation’, ‘estimation in ℓ₁’ and ‘stochastic embedding of undermodelling’. A central theme of this survey is to examine these new methods with reference to the classic bias/variance tradeoff in model structure selection.     

The influence of self-esteem and locus of control on perceived email-related stress

Electronic mail has become an indispensable tool in business and academia, and personal use is increasing every day. However, there is also evidence that Email, unlike more traditional communication media, can exert a powerful hold over its users and that many computer users experience stress as a direct result of email-related pressure. This paper develops a three-fold typology of orientations to email: ‘relaxed’, ‘driven’ and ‘stressed’. It further investigates whether the personality traits of self-esteem and locus of control are associated with email-related stress. It finds that low self-esteem is associated with the ‘driven’ orientation. It further suggests that the ‘stressed’ orientation may be related to how distractive email is perceived to be, compared with other forms of communication.     

A new class of intelligent knowledge-based systems with an optimisation-based inference engine

In this paper we describe a new class of intelligent knowledge-based system (IKBS) which can be used principally for managerial decision making applications. This class of applications often requires a framework for knowledge acquisition which allows the system to use the knowledge of several experts. In addition, since in most business decision making the objective is maximise profits, there is a need for an inference engine which allows optimisation to be carried out. The new class of IKBS which is described in this paper has both these properties, i.e., the ability to use the knowledge of multiple experts in a convenient way and an inference engine which by performing optimisations is able to pick out the profit maximising decisions. As an illustration of these concepts, a system for allocation decision making is described. The system ‘Retail-opt’ allows the user to solve problems like allocation of space in retail outlets, allocation of space in mail order catalogues, pricing policy decisions for discounted airline tickets, etc. In the paper, the basic concepts behind ‘Retail-opt’ are described and an application of ‘Retail-opt’ to the problem of retail space allocation in a Scandinavian Department Store is given. A number of other systems which use these concepts for more complicated competitive decision making situations are also described.     

Visual processing and classification of items on a moving conveyor: a selective perception approach

Many industrial applications require some sort of automated visual processing and classification of items placed on a moving conveyor. In this paper, we present a selective perception based approach to visual processing. The novelty of this approach is that instead of processing the whole image, only areas that are deemed ‘‘interesting’’ and hence calling for attention are analyzed. The attentional sequences thus constructed can then be used for a variety of tasks including shape determination. Since only a small portion of the whole image is processed, visual processing can be real-time and flexible without requiring special hardware. Two different applications based on this approach are described. In a defective item detection task, we explain in detail how attentional sequences can be used. As a second application, the approach has been implemented in an automated remote controller sorter in a TV manufacturing plant—thus confirming its practical applicability.     

The rank one mixed μ problem and ‘kharitonov-type’ analysis

The general mixed μ problem has been shown to be NP hard, so that the exact solution of the general problem is computationally intractable, except for small problems. In this paper we consider not the general problem, but a particular special case of this problem, the rank one mixed μ problem. We show that for this case the mixed μ problem is equivalent to its upper bound (which is convex), and it can in fact be computed easily (and exactly). This special case is shown to be equivalent to the so-called ‘affine parameter variation’ problem (for a polynomial with perturbed coefficients) which has been examined in detail in the literature, and for which several celebrated ‘Kharitonov-type’ results have been proven.     

Bridging the gap between the Kodak and the Flickr generations: A novel interaction technique for collocated photo sharing

Passing around stacks of paper photographs while sitting around a table is one of the key social practices defining what is commonly referred to as the ‘Kodak Generation’. Due to the way digital photographs are stored and handled, this practice does not translate well to the ‘Flickr Generation’, where collocated photo sharing often involves the (wireless) transmission of a photo from one mobile device to another. In order to facilitate ‘cross-generation’ sharing without enforcing either practice, it is desirable to bridge this gap in a way that incorporates familiar aspects of both.In this paper, we discuss a novel interaction technique that addresses some of the constraints introduced by current communication technology, and that enables photo sharing in a way, which resembles the passing of stacks of paper photographs. This technique is based on dynamically generated spatial regions around mobile devices and has been evaluated through two user studies. The results we obtained indicate that our technique is easy to learn and as fast, or faster than, current technology such as transmitting photos between devices using Bluetooth. In addition, we found evidence of different sharing techniques influencing social practice around photo sharing. The use of our technique resulted in a more inclusive and group-oriented behavior in contrast to Bluetooth photo sharing, which resulted in a more fractured setting composed of sub-groups.     

Online safety calculations for glide-slope recapture

As unmanned aerial vehicles (UAVs) increase in popularity and usage, an appropriate increase in confidence in their behavior is expected. This research addresses a particular portion of the flight of an aircraft (whether autonomous, unmanned, or manned): specifically, the recapture of the glide slope after a wave-off maneuver during landing. While this situation is rare in commercial aircraft, its applicability toward unmanned aircraft has been limited due to the complexity of the calculations of safety of the maneuvers. In this paper, we present several control laws for this glide-slope recapture, and inferences into their convergence to the glide slope, as well as reachability calculations which show their guaranteed safety. We also present a methodology which theoretically allows us to apply these offline-computed safety data to all kinds of unmanned fixed-wing aerial vehicles while online, permitting the use of the controllers to reduce wait times during landing. Finally, we detail the live aircraft application demonstration which was done to show feasibility of the controller, and give the results of offline simulations which show the correctness of online decisions at that demonstration.This work was sponsored by the Large National Science Foundation Grant for Information Technology Research (NSF ITR) ‘‘Foundations of Hybrid and Embedded Software Systems’’, Award #0225610, and by Defense Advanced Research Projects Administration (DARPA) ‘‘Software Enabled Control’’ (SEC) Program, under contract #F33615-98-C-3614.