An application of Soft Systems Dynamics Methodology (SSDM)

The paper argues that by combining some of systems dynamics (SD) and soft systems methodology (SSM) stages, within the intellectual framework proposed by soft systems dynamics methodology (SSDM), a systemic methodology developed by Rodriguez-Ulloa, much can be gained in a systemic intervention when tackling complex social problematic situations. A framework for comparing the ontological, epistemological and methodological principles of SD, SSM and SSDM is proposed and the synthesizing role of SSDM is advanced. SSDM ten stages are briefly outlined and a full account of an application on a small Peruvian enterprise is presented. A reflection on SSDM as a systemic intellectual tool is proposed and conclusions together with points for further research are suggested.     

Causal compositional models in valuation-based systems with examples in specific theories

We show that Pearl's causal networks can be described using causal compositional models (CCMs) in the valuation-based systems (VBS) framework. One major advantage of using the VBS framework is that as VBS is a generalization of several uncertainty theories (e.g., probability theory, a version of possibility theory where combination is the product t-norm, Spohn's epistemic belief theory, and Dempster–Shafer belief function theory), CCMs, initially described in probability theory, are now described in all uncertainty calculi that fit in the VBS framework. We describe conditioning and interventions in CCMs. Another advantage of using CCMs in the VBS framework is that both conditioning and intervention can be easily described in an elegant and unifying algebraic way for the same CCM without having to do any graphical manipulations of the causal network. We describe how conditioning and intervention can be computed for a simple example with a hidden (unobservable) variable. Also, we illustrate the algebraic results using numerical examples in some of the specific uncertainty calculi mentioned above.     

电力市场实用稳定性的判定条件

首次把实用稳定性的理论用于电力市场稳定性的研究中.结合Alvarado提出的电力市场动态模型,利用微分代数方程与特征值技术,从理论上研究电力市场的实用稳定性,并且给出了判断电力市场实用稳定、一致实用稳定和实用渐近稳定性的充分条件.利用这些实用稳定性条件,对于Alvarado给出的数值算例,可方便地利用初始数据判断电力市场模型的实用稳定性,并通过实例提供了假设模型中某个参数在电力市场变化中起主要作用,如何控制电力市场模型实用稳定性的方法.最后利用Maple软件包给出了参数变化引起模型实用稳定和不稳定的图形演示.     

The non-codified use of problem structuring methods and the need for a generic constitutive definition

When we use a PSM what is it we are actually doing? An answer to this question would enable the PSM community to considerably enlarge the available source of case studies by the inclusion of examples of non-codified PSM use. We start from Checkland’s own proposal for a “constitutive definition” of SSM, which originated from trying to answer the question of knowing when a claim of SSM use was legitimate. By extending this idea to a generic constitutive definition for all PSMs leads us to propose a self-consistent labelling schema for observed phenomena arising from PSMs in action. This consists of a set of testable propositions, which, through observation of putative PSM use, can be used to assess validity of claims of PSM use. Such evidential support for the propositions as may be found in putative PSM use can then make it back into a broader axiomatic formulation of PSMs through the use of a set-theoretic approach, which enables our method to scale to large data sets. The theoretical underpinning to our work is in causal realism and middle range theory. We illustrate our approach through the analysis of three case studies drawn from engineering organisations, a rich source of possible non-codified PSM use. The combination of a method for judging cases of non-codified PSM use, sound theoretical underpinning, and scalability to large data sets, we believe leads to a demystification of PSMs and should encourage their wider use.     

Dynamical behavior in a stage-structured differential-algebraic prey-predator model with discrete time delay and harvesting

A differential-algebraic model system which considers a prey-predator system with stage structure for prey and harvest effort on predator is proposed. By using the differential-algebraic system theory and bifurcation theory, dynamic behavior of the proposed model system with and without discrete time delay is investigated. Local stability analysis of the model system without discrete time delay reveals that there is a phenomenon of singularity induced bifurcation due to variation of the economic interest of harvesting, and a state feedback controller is designed to stabilize the proposed model system at the interior equilibrium; Furthermore, local stability of the model system with discrete time delay is studied. It reveals that the discrete time delay has a destabilizing effect in the population dynamics, and a phenomenon of Hopf bifurcation occurs as the discrete time delay increases through a certain threshold. Finally, numerical simulations are carried out to show the consistency with theoretical analysis obtained in this paper.     

Effective parameters of cancellous bone

Cancellous bone is a two–component structure consisting of the bone frame and interstitial blood marrow. In the scope of this presentation, the multiscale finite element method is used for its modeling. This method results from a combination of homogenization theory and the theory of finite elements and is based on the calculation of effective material parameters by investigating representative volume elements (RVEs). For the particular kind of material considered here, a cubic two–phase RVE is assumed where the dry skeleton is modeled in different ways. Apart from the variations of the geometry, the influence of the usage of different types of finite elements is studied in this context. Note that the presence of a liquid phase requires dynamic investigation including the viscous phenomena. To this end, acoustic excitation and an analysis in the complex domain are chosen. The method permits calculation of the effective material parameters such as Young's modulus, bulk modulus and Poisson's ratio and furthermore the simulation of the behaviour of the complete bone or of its parts. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Using Prompted Praxis to Improve Teacher Professional Development in Culturally Diverse Schools

Recent science and teacher education reports continue to stress the need for radical changes in the way teachers are prepared to teach science to diverse learners. In response, a three‐year intervention project was developed to help teachers in culturally diverse schools transform their science teaching practices using learning technologies. Many challenges arose that called for strategies to further manage the progress of the project. This paper describes how one of those strategies, “prompted praxis,” was used to manage two of the main challenges encountered, the teachers' following through with their professional development goals and our own sense of urgency to effect change.     

Identifying the Causal Effects of Stochastic Interventions by Augmented Causal Networks

Suppose that the cause-effect relationships between variables can be described by a causal network. To identify the causal effect of a stochastic intervention, an augmented causal network for stochastic intervention is proposed in this paper. Then, we obtain two graphical criteria for identifying the causal effects of stochastic interventions from passive observations on observed variables only. When either of the two criteria is satisfied, a simple closed-form expression is provided for the causal effect of a stochastic intervention, which enables researchers to assess the causal effect with little effort.     

Messing about in transformations: Structured systemic planning for systemic solutions to systemic problems

The literature on multimethodology indicates that cognitive mapping is relevant to enriching the preliminary, information-gathering phase of Soft Systems Methodology (SSM), and especially the rich picture. By noting the structural complementarity evidenced between SSM’s transformations and the bipolar constructs used in the cognitive mapping methodology known as Strategic Options Development and Analysis (SODA), this paper shows how SODA can be applied beyond SSM’s initial stage, and much more analytically within the heart of SSM, to guide the manner in which a systemic resolution to a problematic situation may be approached. It is proposed, and illustrated through examples, that a SODA map of large numbers of transformations, resulting from an exercise in SSM, offers a methodological means for structuring what might otherwise be perceived as a mess. The paper discusses how in such cases ‘strategic options development and analysis’ of transformations, or SODA-T maps, serve, among other things, to identify relations between transformations, their hierarchies and priorities, problem epicenters and starting points for intervention. In addition, the arsenal of graph theory can be used to cut through what would otherwise appear as interlinked chaos requiring structured operationalization. In this respect, the SODA-T map offers a high-level connective orientation which can guide the interconnections between the respective human activity systems of the transformations, resulting in the final systemic plan. Ultimately, SODA-T mapping is shown to facilitate a structured approach toward systemic planning.     

A weighted causal theory for acquiring and utilizing open knowledge

Motivated by enabling intelligent robots/agents to take advantage of open-source knowledge resources to solve open-ended tasks, a weighted causal theory is introduced as the formal basis for the development of these robots/agents. The action model of a robot/agent is specified as a causal theory following McCain and Turner's nonmonotonic causal theories. New knowledge is needed when the robot/agent is given a user task that cannot be accomplished only with the action model. This problem is cast as a variant of abduction, that is, to find the most suitable set of causal rules from open-source knowledge resources, so that a plan for accomplishing the task can be computed using the action model together with the acquired knowledge. The core part of our theory is constructed based on credulous reasoning and the complexity of corresponding abductive reasoning is analyzed. The entire theory is established by adding weights to hypothetical causal rules and using them to compare competing explanations which induce causal models satisfying the task. Moreover, we sketch a model theoretic semantics for the weighted causal theory and present an algorithm for computing a weighted-abductive explanation. An application of the techniques proposed in this paper is illustrated in an example on our service robot, KeJia, in which the robot tries to acquire proper knowledge from OMICS, a large-scale open-source knowledge resource, and solve new tasks with the knowledge.     

Using abell's narrative method to build a theory: The case of the theory of distributive justice and its generalization to the theory of comparison processes

This paper examines the usefulness for theoretical work of the narrative method proposed by Peter Abell. Our assessment proceeds by using the narrative method to perform the two main tasks of theoretical analysis—constructing postulates and deriving predictions. Tb illustrate, we focus on the theory of distributive justice and the more general theory of comparison processes to which it led. The results of our assessment of the usefulness of Abell's narrative method for theoretical work indicate that the narrative method has far wider applicability than Abell has claimed for it. For example, (i) it is useful for all theoretical work in the sociobehavioral sciences, not only for theoretical work based on game theory, (ii) it is useful for analyzing thought‐experiments as well as narrative accounts of actual actions and events, and (iii) the events in the narrative need not be restricted to human actions but can include events not traceable to human agency. We conclude also that Abell's narrative method complements the use of mathematical analysis in theoretical work and that it may be especially valuable for theoretical derivation involving two or more theories jointly.     

Asymptotic behavior of dynamic equations ontime scales

As a way to unify a discussion of many kinds of problems for equations in the contionous and discrete case(but also in order to reveal discrepancies between both cases), a theory of "time scales" was proposed and developed by Sulbach and Hilger. In our paper we investigate the asymptoic behaviour of so-called dynamic equations on time scales, and sych dynamic equations are differentialequations in the continous case and difference equations in the discrete case. We offer a perturbation result that leads to a time scales version of Levinson's Fundamental Lemma. Crucial are a dichotomy condition and a growth condition on the perturbation. Also, in the case that Levinson's result cannot be applied immediately, we suggest several preliminary transformations that might lead to a situation where Levinson's lemma is applicable. Such tranformations have been suggested by Harris and Lutz in the continuous case and by Benzaid and Lutz in the discrete case. Both those cases are covered by our theory, plus cases "in between". Examples for such cases will also be discussed in this paper.     

A model of speculative behaviour with a strange attractor

An asset pricing model for a speculative financial market with fundamentalists and chartists is analysed. The model explains bursts of volatility in financial markets, which are not well explained by the traditional finance paradigms. Speculative bubbles arise as a complex non-linear dynamic phenomenon brought about naturally by the dynamic interaction of heterogeneous market participants. Depending on the time lag in the formation of chartists' expectations, the system evolves through several dynamic regimes, finishing in a strange attractor. Chaos provides a self-sustained motion around the rationally expected equilibrium that corresponds to a speculative bubble. In order to explain the role of Chartism, chaotic motion is a very interesting theoretical feature for a speculative financial market model. It provides a complex non-linear dynamic behaviour around the Walrasian equilibrium price produced by deterministic interactions between fundamentalists and chartists. This model could be a link between two opposite views over the behaviour of financial markets: the theorist's literature view that claims the random motion of asset prices, and the chartist's position extensively adopted by market professionals.     

Kinematical synthesis of 1-dof mechanisms using finite elements and genetic algorithms

The use of finite elements in both kinematic analysis and synthesis of mechanisms has shown good performance. Its only drawback is the need for an initial reasonable quality solution.

To address this topic, the use of genetic algorithms with a finite-element-based error function is proposed in this paper. This approach has not only shown good behaviour with simple mechanisms, but also with complex kinematic chains.

The energy-based error function, which has demonstrated such good behaviour in the optimization via second-order Newton–Raphson methods, presented some limitations. To solve them, a new distance-based error function has been developed. Simultaneously, new finite elements have been created to represent some joints and kinematic elements. The need to address some specific configuration problems has led to the development of a correction algorithm.     

A dynamic binomial expansion technique for credit risk measurement: a Bayesian filtering approach

Credit risk measurement and management are important and current issues in the modern finance world from both the theoretical and practical perspectives. There are two major schools of thought for credit risk analysis, namely the structural models based on the asset value model originally proposed by Merton and the intensity‐based reduced form models. One of the popular credit risk models used in practice is the Binomial Expansion Technique (BET) introduced by Moody's. However, its one‐period static nature and the independence assumption for credit entities' defaults are two shortcomings for the use of BET in practical situations. Davis and Lo provided elegant ways to ease the two shortcomings of BET with their default infection and dynamic continuous‐time intensity‐based approaches. This paper first proposes a discrete‐time dynamic extension to the BET in order to incorporate the time‐dependent and time‐varying behaviour of default probabilities for measuring the risk of a credit risky portfolio. In reality, the ‘true’ default probabilities are unobservable to credit analysts and traders. Here, the uncertainties of ‘true’ default probabilities are incorporated in the context of a dynamic Bayesian paradigm. Numerical studies of the proposed model are provided.     

The effect of environmental parameters on product recovery

Economical and environmental issues are the main driving forces for the development of closed-loop supply chains. This paper examines the impact of environmental issues on long-term behaviour of a single product supply chain with product recovery. The environmental issues examined are the firm's `green image' effect on customer demand, the take back obligation imposed by legislation, and the state campaigns for proper disposal of used products. The behaviour of the system is analyzed through a dynamic simulation model based on the principles of the system dynamics (SD) methodology. This model includes all major inventories of new, used and recovered products and the flows among them. Inventory levels and flow rates are linked through differential equations. The dynamic model provides an experimental simulation tool, which can be used to evaluate the effect of environmental issues on long-term decision making in collection and remanufacturing activities and on product demand. Numerical analysis illustrates the potential uses of the methodology.     

An analytical dynamic model for single-cracked beams including bending,axial stiffness,rotational inertia,shear deformation and coupling effects

This paper develops an analytical dynamic model for cracked beams including bending, axial stiffness, rotational inertia, shear deformation and the coupling of the last two effects. The damage is modelled using a rotational spring that simulates the crack based on fracture mechanics theory. The developed model is used to predict variations on natural frequencies for several crack sites and damage magnitude along the beam. The importance of this work lies in the development of an analytical model that has no approximation due to discretization of the displacement field. This initial theoretical approach describes the expected behaviour for changes in the natural frequencies for simply-supported and clamped-free beams with the precision that only analytical methods allow. The results provide a useful benchmark to compare with approximate numerical methods that can be used to model and analyse the problem. The model showed similar results for long span beams, but the inclusion of rotational inertia and shear deformation effects rendered improvements in the dynamic behaviour mainly in the case of slender and short span beams when compared with the simplified Euler–Bernoulli model.     

Problem structuring in project management: an application of soft systems methodology (SSM)

Recent research suggests a major role for problem structuring methods (PSMs) in the field of project management, particularly at the front-end of projects, where objectives are often unclear and where different constituencies have conflicting aims. This paper presents a case example of soft systems methodology (SSM) at the front-end of a major project within Tesco Stores Ltd. A detailed account of the intervention is given, including the results achieved and a discussion of how the methodology was used for multiple purposes within the same intervention. Within the literature, there remains a lack of detailed examples from which people can learn more about the use of PSMs in project management. By providing a detailed example of SSM in action, this paper seeks to highlight the importance of problem structuring at the front-end of projects and the potential role an approach such as SSM can play at this crucial stage.     

The Use of Soft Systems Methodology in Practice

This paper reports the results of a survey intended to discover the extent to which Checkland's Soft Systems Methodology (SSM) is used in practice. Some 300 questionnaires were sent to people who had had some exposure to SSM and, surprisingly, nearly half were returned. The majority described in detail their uses of SSM and most felt that it had been successful. This paper describes the overall quantitative results from the survey as well as presenting a qualitative analysis of the experiences of using SSM.