A fuzzy PLC with gain-scheduling control resolution for a thermal process – a case study

This paper presents a case study on the practical implementation of a fuzzy-PLC system for a thermal process. The theoretical study indicates that the inferior performance of fuzzy-controlled processes around a reference point is often caused by insufficient resolution of the fuzzy inference. The limitations of ladder logic cannot support complex algorithms for resolution improvement. A simple gain adaptation method is presented here, to achieve smooth fuzzy control, that can be easily implemented in a PLC system. Real-time experiments on an unidentified thermal process show the effectiveness of the approach, as well as the robustness of the fuzzy controller with respect to the time-varying features of the process.     

Optimization of process parameters through fuzzy logic and genetic algorithm – A case study in a process industry

The simultaneous generation of steam and power, which is commonly referred to as cogeneration, has been adopted by many sugar mills in India to overcome the power shortage. It becomes an increasingly important source of income for sugar factories. The problems faced by the sugar mill industry arise mainly due to failures of either the complete system or some specific components during the cogeneration process. This paper presents the failure analysis of the boiler during the cogeneration process and provides solution to overcome these failures. The failures frequently occur in the screw conveyor and in the drum feeder of fuel feeding system and the grate of the boiler. In this research work, the statistical tools viz., Failure Mode and Effect Analysis (FMEA) and the Taguchi method have been applied to investigate and alleviate these failures. Since conventional FMEA has some limitations and Taguchi method does not give better solution, fuzzy FMEA has been employed to overcome the limitations and genetic algorithm technique has been applied to obtain failure – free system during the cogeneration process.     

Correlating mobile phone usage and travel behavior – A case study of Harbin,China

Information and communication technologies (ICTs), such as mobile phones and the Internet, are increasingly pervasive in modern society. These technologies provide new resources for spatio-temporal data mining and geographic knowledge discovery. Since the development of ICTs also impacts physical movement of individuals in societies, much of the existing research has focused on examining the correlation between ICT and human mobility. In this paper, we aim to provide a deeper understanding of how usage of mobile phones correlates with individual travel behavior by exploring the correlation between mobile phone call frequencies and three indicators of travel behavior: (1) radius, (2) eccentricity, and (3) entropy. The methodology is applied to a large dataset from Harbin city in China. The statistical analysis indicates a significant correlation between mobile phone usage and all of the three indicators. In addition, we examine and demonstrate how explanatory factors, such as age, gender, social temporal orders and characteristics of the built environment, impact the relationship between mobile phone usage and individual activity behavior.     

Bridges and barriers to hardware-dependent software ecosystem participation – A case study

BackgroundSoftware ecosystems emerged as means for several actors to jointly provide more value to the market than any of them can do on its own. Recently, software ecosystems are more often used to support the development of hardware-dependent solutions.ObjectivesThis work aims at studying barriers and bridges to participation in an ecosystem with substantial hardware dependencies.MethodWe conducted an interview-based case study of an ecosystem around Axis’ network video surveillance systems, interviewing 10 internal experts and 8 external representatives of 6 companies, complemented by document studies at Axis.ResultsMajor bridges to the ecosystem include end customer demands, open and transparent communication and relationship, as well as internal and external standardizations. Barriers include the two-tier business model, entry barriers and execution performance issues. Approximately half of the identified bridges and barriers could be considered hardware-dependent ecosystems specific.ConclusionOur results suggest that ecosystem leaders should share their sales channels with the ecosystem participants and focus on good communication and relationships as the dominant factors for the ecosystem participation. Moreover, we report that internal and external standardization can play a dual role, not only ease the development but also enable additional sales channels and new opportunities for the ecosystem participants. At the same time, the business model selected by the ecosystem leaders and performance, are identified as the main barriers to ecosystem participation. We believe that the business model barrier may be much more important for similar hardware-dependent software ecosystems.     

Failures in fault-tolerant FPGA-based controllers – A case study

Nowadays, FPGA-based Networked Control Systems (NCSs) are frequently used. Transient and permanent faults occur often as a result of radiation in industrial environments. Accordingly, Fault-Tolerant (FT) FPGA-based NCSs are desired. In this paper, a novel NCS model is proposed composing of In-Loop and S2A architectures linked via an Ethernet switch. This architecture is used in shape detection machines with vision sensing requirements. FT techniques are applied in the controller nodes of the system along with Dynamic Partial Reconfiguration (DPR) for FPGA-based controller recovery. The reliability of the system due to changes in both the recovery rate and the conditional probability of failure occurrence (either transient or permanent), is presented in this paper. Accordingly, a Markov model is constructed for reliability calculations. A case study is used to illustrate the use of such a model to choose appropriate maintenance strategies as well as a quantitative measure for the ability of the FT techniques to increase system reliability. Coverage is then studied in the context of the same system. Furthermore, system failures are divided into safe system failures and unsafe system failures. Another Markov model is developed. Then, a case study is used to illustrate the effect of coverage on the probability of occurrence of an unsafe system failure.     

A case study in class library verification: Java’s vector class

This paper presents a verification of an invariant property for the Vector class from JAVA’s standard library (API). The property says (essentially) that the actual size of a vector is less than or equal to its capacity. It is shown that this “safety” or “data integrity” property is maintained by all methods of the Vector class, and that it holds for all objects created by the constructors of the Vector class. The verification of the Vector class invariant is done with the proof tool PVS. It is based on a semantics of JAVA in higher order logic. The latter is incorporated in a special purpose compiler, the LOOP tool, which translates JAVA classes into logical theories. It has been applied to the Vector class for this case study. The actual verification takes into account the object-oriented character of JAVA: (non-final) methods may always be overridden, so that one cannot rely on a particular implementation. Instead, one has to reason from method specifications in such cases. This project demonstrates the feasibility of tool-assisted verification of non-trivial properties for non-trivial JAVA classes. Published online: 10 May 2001     

A spatial system dynamic model for regional desertification simulation – A case study of Ordos,China

A spatial system dynamic (SSD) model for simulating desertification was developed by integrating climate, soil water, population, economy, pasturage, and land use. Net Primary Production (NPP) was selected as an intermediate variable to measure the impacts of driving forces and desertification grades. Ordos in China was selected to test the model. Ten scenarios were designed to simulate desertification dynamics in Ordos from 2011 to 2030. The results showed that the SSD model was reliable, and the overall accuracy of desertification degree was approximately 83%. Climate factors had relatively higher sensitivities than other parameters. Although humid climate and sustainable development strategy would reduce desertified land area and desertification degree before 2025, the rapid increase in pasturage pressure would offset this trend. Arid climate and unsustainable development strategy would accelerate desertification expansion. For local government, it is necessary to persist in the present desertification prevention policy and completely banned grazing after 2025.     

Operational release planning in large-scale Scrum with multiple stakeholders – A longitudinal case study at F-Secure Corporation

ContextThe analysis and selection of requirements are important parts of any release planning process. Previous studies on release planning have focused on plan-driven optimization models. Unfortunately, solving the release planning problem mechanistically is difficult in an agile development context.ObjectiveWe describe how a release planning method was employed in two case projects in F-Secure, a large Finnish software company. We identify the benefits which the projects gained from the method, and analyze challenges in the cases and improvements made to the method during the case projects.MethodWe observed five release planning events and four retrospectives and we conducted surveys in the first two events. We conducted six post-project interviews. We conjoined the observation notes, survey results and interviews and analyzed them qualitatively and quantitatively.ResultsThe focal point of the method was release planning events where the whole project organization gathered to plan the next release. The planning was conducted by the development teams in close collaboration with each other and with the other stakeholders. We identified ten benefits which included improved communication, transparency, dependency management and decision making. We identified nine challenges which included the lacking preparation and prioritization of requirements, unrealistic schedules, insufficient architectural planning and lacking agile mindset. The biggest improvements to the method were the introduction of frequent status checks and a big visible planning status board.ConclusionThe release planning method ameliorated many difficult characteristics of the release planning problem but its efficiency was negatively affected by the performing organization that was in transition from a plan-driven to an agile development mindset. Even in this case the benefits clearly outweighed the challenges and the method enabled the early identification of the issues in the project.     

A stepwise cluster analysis approach for downscaled climate projection – A Canadian case study

Downscaling techniques are used to obtain high-resolution climate projections for assessing the impacts of climate change at a regional scale. This study presents a statistical downscaling tool, SCADS, based on stepwise cluster analysis method. The SCADS uses a cluster tree to represent the complex relationship between large-scale atmospheric variables (namely predictors) and local surface variables (namely predictands). It can effectively deal with continuous and discrete variables, as well as nonlinear relations between predictors and predictands. By integrating ancillary functional modules of missing data detecting, correlation analysis, model calibration and graphing of cluster trees, the SCADS is capable of performing rapid development of downscaling scenarios for local weather variables under current and future climate forcing. An application of SCADS is demonstrated to obtain 10 km daily mean temperature and monthly precipitation projections for Toronto, Canada in 2070–2099. The contemporary reanalysis data derived from NARR is used for model calibration (1981–1990) and validation (1991–2000). The validated cluster trees are then applied for generating future climate projections.     

Enabling metrology-oriented specification of geometrical variability – A categorical approach

In this paper a metrology-oriented specification schema is proposed to enrich the specification semantics with sufficient metrological information. It is designed particularly for applications where non-traditional measurement methods are applied; and it can also identify any redundancies, inconsistencies or incompletenesses of a specification. The proposed schema is based on category theoretical semantics which uses category theory as the foundation to model the semantics. A set of verification operations that derived from the measurement process was firstly formalised using the categorical semantics. Then a set of full faithful functors were constructed to map the set of verification operations to a set of specification operations. A set of simplification rules was then developed to deduce all of the necessary specification objects which are independent to each other. Then the residual specification objects provide a compact structure of the specification. Three test cases were conducted to validate the proposed schema. An industrial computed tomography (CT) measurement process for an impeller manufacturing using selective laser sintering (SLS) technique, was modelled and a set of independent specification elements was then deduced. The other two test cases for checking redundancy and incompleteness on general ISO specifications were carried out. The results show that the proposed schema works for proposing semantic enriched specification that are characterised by non-traditional measurement methods and for testing redundancy and incompleteness of specifications based on geometrical product specifications and verification (GPS) standards system.     

The generic model query language GMQL – Conceptual specification,implementation, and runtime evaluation

The generic model query language GMQL is designed to query collections of conceptual models created in arbitrary graph-based modelling languages. Querying conceptual models means searching for particular model subgraphs that comply with a predefined pattern query. Such a query specifies the structural and semantic properties of the model fragment to be returned. In this paper, we derive requirements for a generic model query language from the literature and formally specify the language’s syntax and semantics. We conduct an analysis of GMQL׳s theoretical and practical runtime performance concluding that it returns query results within satisfactory time. Given its generic nature, GMQL contributes to a broad range of different model analysis scenarios ranging from business process compliance management to model translation and business process weakness detection. As GMQL returns results with acceptable runtime performance, it can be used to query large collections of hundreds or thousands of conceptual models containing not only process models, but also data models or organizational charts. In this paper, we furthermore evaluate GMQL against the backdrop of existing query approaches thereby carving out its advantages and limitations as well as pointing toward future research.     

Conceptualizing task-technology fit and the effect on adoption – A case study of a digital textbook service

Although information technology has revolutionized virtually every aspect of how we interact with products and services, it has changed learning to a surprisingly small degree. In a study of a digital textbook service, we provide a new conceptual definition and measurement of technology fit. We conceptualize task-technology fit as how well a technology is integrated with a set of interrelated tasks included in achieving the goal of the behavior where the technology is used. Whereas research on technology adoption typically explains around 40 percent of the variance in motivation to adopt, our model explains as much as 76 percent.     

Career anchors and disturbances in job turnover decisions – A case study of IT professionals in Taiwan

Previous models of turnover by IT professionals consider job satisfaction as a key indicator. One common model considers whether an organization matches the internal anchors of IT employees to provisions in the work place. This pattern is often broken by other considerations that disturb the relationship between job satisfaction and intent to seek employment elsewhere. Such disturbances present a problem in planning and are not globally considered in research models. A qualitative study of ten cases yields new insight into the disturbances that break the pattern leading to a more general model of turnover.     

Optimizing a damped system – a case study

We consider a second-order damped-vibrational system described by the equation M ?+C(v) [xdot]+K x=0, where M, C(v), K are real, symmetric matrices of order n. We assume that the undamped eigenfrequencies (eigenvalues of (λ² M+K) x=0) ω₁, ω₂, …, ω _n , are multiple in the sense that ω₁=ω₂, ω₃=ω₄, …, ω _n?1=ω _n , or are given in close pairs ω₁ ≈ ω₂, ω₃ ≈ ω₄, …, ω _n?1 ≈ ω _n . We present a formula which gives the solution of the corresponding phase space Lyapunov equation, which then allows us to calculate the first and second derivatives of the trace of the solution, with no extra cost. It can serve for the efficient trace minimization.     

Understanding consumers’ continuance intention towards mobile purchase: A theoretical framework and empirical study – A case of China

Although mobile purchase is convenient in the age of mobile commerce, many consumers still do not utilize mobile purchase to its full potential. From the mobile vendor’s perspective, retaining current customers and facilitating their continued purchase are crucial to create profitability and achieve a sustainable development. An understanding of the continuance intention towards mobile purchase can provide insights into mobile vendors’ marketing campaigns. Therefore, it is important to examine the determinants that impact continuance intentions of consumers for mobile purchase. Drawing upon information success model, flow theory and trust, this study proposed and empirically tested an integrated model to better understand the determinants of consumers’ continued intention to purchase on mobile sites. Empirical data from 462 users who had experience with mobile purchase were tested against the proposed research model by using structural equation modelling (SEM). The results indicated that information quality, and privacy and security concerns are the main factors affecting trust, whereas service quality is the main factor affecting flow. System quality, and privacy and security concerns affect satisfaction. Trust affects flow, which in turn affects satisfaction. These three factors together affect continued intention towards mobile purchase. The findings of this study provide several important implications for mobile commerce research and practice.     

Fractional Wishart processes and ε-fractional Wishart processes with applications

In this paper, we introduce two new matrix stochastic processes: fractional Wishart processes and $\epsilon$-fractional Wishart processes with integer indices which are based on the fractional Brownian motions and then extend $\epsilon$-fractional Wishart processes to the case with non-integer indices. Both processes include classic Wishart processes (if the Hurst index $H$ equals $\frac{1}{2}$) and present serial correlation of stochastic processes. Applying $\epsilon$-fractional Wishart processes to financial volatility theory, the financial models account for the stochastic volatilities of the assets and for the stochastic correlations not only between the underlying assets’ returns but also between their volatilities and for stochastic serial correlation of the relevant assets.     

CLPS–B – A constraint solver to animate a B specification

This paper proposes an approach to evaluating B formal specifications using constraint logic programming with sets (CLPS). This approach is used to animate and generate test sequences from B formal specifications. The solver, called CLPS–B, is described in terms of constraint domains, consistency verification, and constraint propagation. It is more powerful than most constraint systems because it allows the domain of variable to contain other variables, which increases the level of abstraction. The constrained state propagates the nondeterminism of the B specifications and reduces the number of states in a reachability graph. We illustrate this approach by comparing the constrained state graph exploration with the concrete one in a simple example – process scheduler. We also describe the automated test generation method that uses the CLPS–B solver to better control combinational explosion.     

Acceptance of software process innovations – the case of extreme programming

Extreme programming (XP), arguably the most popular agile development methodology, is increasingly finding favor among software developers. Its adoption and acceptance require significant changes in work habits inculcated by traditional approaches that emphasize planning, prediction, and control. Given the growing interest in XP, it is surprising that there is a paucity of research articles that examine the factors that facilitate or hinder its adoption and eventual acceptance. This study aims to fill this void. Using a case study approach, we provide insights into individual, team, technological, task, and environmental factors that expedite or impede the organization-wide acceptance of XP. In particular, we study widely differing patterns of adherence to XP practices within an organization, and tease out the various issues and challenges posed by the adoption of XP. Based on our findings, we evolve factors and discuss their implications on the acceptance of XP practices.     

Customer participation,value co-creation and customer loyalty – A case of airline online check-in system

Information communication technologies and self-service technologies, such as self-check-in kiosks or online check-in systems, are widely used in the air transport industry. This study proposes a conceptual model to investigate the relationships among customer participation, co-created values and customer loyalty in an air transport context, and empirically tests the model by using questionnaire survey data collected from Taiwanese airline passengers. In particular, three perceived values (i.e. enjoyment value, economic value and relational value) are specified to represent the passengers' co-created values. The empirical results support the following hypotheses. Customer participation in using an online check-in system is positively related to all three values, which further lead to satisfaction with respect to the system. System satisfaction is also related to satisfaction with respect to the company, and both system satisfaction and company satisfaction have positive effects on customer loyalty.     

Knowledge specification and representation for an “intelligent” interface devoted to process monitoring and supervision

This paper presents our approach of cooperation between a human operator and a decision aid tool by means of an “intelligent” interface manager: the Decisional Module of Imagery (D.M.I.). The “heart” of the D.M.I. is an expert system which manipulates three main objects (the WHAT, WHEN and HOW objects) described next. Knowledge specification and representation for the expert system, and the way we chose to implement it, are then explained.