System Design Phase Research Articles

Availability centred maintenance for offshore wind farms

Purpose – Maintenance planning is a complicated decision-making process that involves the major stakeholders and the main life-cycle phases of an engineering system. The purpose of this paper is to propose an availability-centred maintenance planning approach for offshore wind farms, with special focus on the early system design phase. Design/methodology/approach – The proposed approach is based on a stepwise procedure that integrates logistics consideration into reliability-centred maintenance. For each step, the essential methods for systematic analysis and documentation are introduced. Findings – Practical information from current offshore wind farms and lessons learned from relevant industries are included to exemplify and justify the implementation of the proposed approach. In a general way, the approach shows that valuable input can be provided to decision making about maintainability and maintenance planning. Furthermore, the approach facilitates the initial maintenance plan to be adjusted and improved upon as additional operating experience becomes available. Research limitations/implications – Offshore wind energy is still an industry in its infancy with an attendant high degree of confidentiality. There is scarcely any detailed practical information available for the production of a case study on this topic. However, the current paper’s theoretical basis may be applied to identify current and future knowledge gaps, for the development of more detailed guidelines as established in the further research. Originality/value – Maintenance planning of offshore wind farms is an area of current interest, although often the focus is on achieving cost reductions and not on the formal development of such a systematic approach as conceived in this paper.

Robust series–parallel systems design under combined interval–ellipsoidal uncertainty sets

System reliability is an important requirement in design stage of systems, which depends on some parameters such as components’ reliabilities which are estimated in advance. Due to some factors, the estimated reliabilities for components may vary during and prior to implementation. Therefore, it is important to consider various controllable and uncontrollable factors, which influence the system reliability, in the design phase of systems. Consequently, the need for presenting robust designs, which are insensitive or less sensitive to these variations, is necessary in the area of system engineering. In most cases especially for new and evolving systems, or for strategic design of systems, less or no historical data are available. Therefore, stochastic, fuzzy or interval programming approaches are no longer applicable to consider the uncertainty. In this paper, for the first time an uncertainty set in the form of combined interval–ellipsoidal is considered to study the behavior of variations. A robust optimization approach is employed to deal with this kind of uncertainty in reliability optimization problems. The findings indicate that applying the proposed robust reliability models, results in robust and reliable designs in practice which is crucial for many systems such as medical systems, nuclear systems and the like.

Structural feedback analysis of a hearing aid using finite element and lumped parameters methods

Hearing aids are designed to overcome hearing losses suffered by some individuals and operated by measuring and amplifying the acoustic field at certain frequency depending on the user hearing loss. In many cases, its transducers (microphone and loudspeaker) are near located, and a feedback signal phenomenon may occur, either through structural or airborne transmission. The structural feedback is characterized by a vibrational response at the microphone position produced by the loudspeaker, also called receiver, that result in a unwanted signal due to the microphone vibration sensitivity. If not properly controlled, the feedback signal builds up, resulting in a loud whistle at the user ear causing great discomfort. The objective of this work is to analyse the structural feedback mechanism at a behind-the-ear hearing aid, and proposed a numerical approach that allows the consideration of the phenomena during the design phase of such systems. A numerical model, based on the finite element method (FEM) and the lumped parameters method, was used to analyse and quantify the problem. While the hearing aid case was modelled using FEM, the receiver and its suspensions were represented by means of a single degree-of-freedom or a multiple degree-of-freedom systems. The procedures used to define material properties and dynamic parameters are presented and discussed. Experimental tests are used to validate the models separately and to determine vibration levels imposed at the microphone location during the hearing aid operation, which are used to verify the overall accuracy of the numerical model. Finally, a sensitivity analysis is performed, indicating some design options that can be used to minimize the structural feedback problem in hearing aids.

Component redundancy allocation in optimal cost preventive maintenance scheduling

This work presents a methodology to assist maintenance teams in defining the maintenance schedule and redundancy allocation that minimise the life-cycle average cost of a system. The minimal data required are three average costs and one reliability function. This methodology is useful in a system design phase, since in this situation data is usually scarce or inaccurate, but can also be applied in the exploration phase. It consists of an adaptation of the classical optimal age replacement method, combined with a redundancy allocation problem. A set of simple illustrative examples covering a variety of operating conditions is presented, demonstrating quantitatively the applicability of the methodology to a range of maintenance optimisation decisions.

Early Energy Estimation of Networked Embedded Systems Executing Concurrent Software Components

2 Abstract—This paper presents and evaluates a new approach of modeling energy consumption of embedded systems resulted by concurrent software components. The objective is to enable energy estimation within early phases of system development, which allows system designers to compare different allocations of software components within networked systems. The model is presented in detail and its application demo started by a case study. Additionally, an execution time estimation for software components is presented which is necessary for the energy model - but previously not available. The model was developed being applicable early in the development process, i.e. previous to any software implementation. This was realized by using only available information. The individual elements of the presented model are: energy consumption of software components themselves, energy consumption resulted by any software component, and energy consumption resulted by specific software components. The variables of the model can be estimated during early phases of system design using existing methods, expecting the execution time of software components. For that reason, a previously energy estimation technique (1) was further developed to estimate the execution time based on program flowcharts. The estimation was verified by using three commercially available benchmarks. The flowcharts of these are utilized to estimate the execution times. The comparison between estimated and measured execution time of an exemplary embedded system results in an estimation error bandwidth between -12.5 % and +6.8 %. Additionally, an algorithm is presented which enables an automated analysis of program flowcharts as part of the execution time estimation. The developed model was applied within an automotive case study which shows a theoretical energy saving potential of 36.2 %. This demonstrates the potential and relevance of modeling energy estimation within early development phases.

The Global Track&Trace System for food: General framework and functioning principles

This paper describes the Global Track and Trace System (GTTS) developed for supporting the management of food traceability along the food supply chain, from the primary producer to the final consumer. The main goal of GTTS is to support the different users involved in a food supply chain and assist in the process of traceability management. The informative system has been developed taking into account the different features of a food supply chain. A general framework has been generated for supporting future evolutions and customizations. Different steps, which involve the phases of supply chain analysis, supply chain modelling, data analysis and data modelling, are at the base of the methodological approach followed during the phase of system design and development. The solution adopted for the information management is generally applicable, which means that it meets the requirements of different types of food industries. The model can be applied in real-life situations that might benefits from the traceability solution.

Modeling of Safety-Critical Systems Using Petri Nets

Safety plays a crucial role in the development of complex computer systems in the relevant areas like railway transport, process industry, power plants, etc. In the design phase of safety-critical systems, various methods are used to make the system work correctly. Due to advancements in technology, safety-critical systems are equipped with the necessary safety precautions but not completely. The malfunctioning of systems may lead to catastrophic accidents. Compared to commonly used safety-analysis approaches like Failure Mode and Effects Analysis, Fault Tree Analysis, Event Tree Analysis, etc., Petri Nets are more suitable for hazard analysis as they can specify data flow and stochastic interdependencies. An example safety-critical system, Railroad Crossing Junction has been modeled using Petri Nets for hazard analysis to detect the occurrences of possible hazards in the system. The proposed modeling framework provides a flexible graphical representation allowing a qualitative analysis based on the safe and unsafe state representations and a quantitative analysis based on the reachability graph that in turn leads to an effective safety analysis. The result of careful and rigorous safety analysis is to identify unsafe states. The results of safety analysis can be used by the designer for re-designing the system to improve safety. The designer of the system needs to repeat the process to detect the unsafe states.

Design of a Component Interface Complexity Measurement Tool for Component-Based Systems

Component-based systems encompass software systems that are built by assembling different components procured from different sources. These components work together in a component assembly to achieve the defined task. The component interfaces are the only means for determining the complexity of the component, when the source code is not available. The complexities of the interfaces of these components depend on the structures of the interfaces, the constraints that are imposed and the interactions of these components through their interfaces. As such, the complexities of these components can be measured by way of their interfaces, at an early stage of the system design phase. Traditional complexity metrics are not capable of capturing all the essential characteristics of component-based systems. Therefore, new metrics suitable for component-based development have been proposed in the literature. This paper proposes an upgraded version of a tool, which was developed and is capable of extracting structural complexity metrics for component interfaces directly from Unified Modeling Language design specifications. The tool measures three essential characteristics of a component-based system, e.g. interfaces, constraints and interactions, which are the primary contributors to the complexity of component-based systems. We demonstrate the extraction of structural complexity metrics through a case study of a University Case Registration System.

Assessing the reliability of components with micro- and nano-structures when they are part a multi-scale system

Products with macro- and meso-scales components have grown into multi-scale systems where some of their components have shrunk to a smaller scale such as micro- and nano-structures. In practice, engineers may be unable to accurately assess their designs to improve the reliability of components in multi-scale systems, because component parts with micro- and nano-structures cannot be realized directly in system design phase. Thus, all kinds of design processes such as engineering verifications for physics or functions become increasingly complex in a muti-scale system. For this shortcoming, we present a parametric Bayesian method that enables engineers to assess indirectly the reliability and the quality of a component with either a micro-structure or a nano-structure using experimental data on failure time of the multi-scale system. Our proposed Bayesian approach is flexible in allowing a general model for distributions of failure times of a multi-scale system and its components. Our method is applied to a simulated data set.

Assembly Modelling and Time estimating during the early phase of Assembly Systems Design

An approach for assembly time estimating following sequence and process modelling since the conceptual phase of new assembly systems design is proposed in this work. The purpose is to support the decision about their levels of automation (LoA) following a dedicated modelling language labeled ASML offering a better visibility about processes design and analyses. ASML provides an easy way of defining several systems alternatives based on an initial ASML model representing assembly motions using a standard vocabulary and structured executing architectures. The correlation of early phase modelling with time estimating proposed in this paper to support LoA decision is up to us new to the literature. The approach of modelling and time estimating was tested on assembly examples and a computerized tool was also developed and tested. Several related applications such as processes time performances evaluating, time savings, productivity assessment, lines balancing, and cost estimating are proposed as well as other possible future applications presented as perspectives and future works that can be supported by the defined environment dedicated to early phase assembly systems design and automation decision.

A Markov Decision Process Approach to Dynamic Power Management in a Cluster System

Dynamic power management (DPM) plays a significant role to save power consumption effectively in both the design and operational phases of computer-based systems. It is well known that the state-dependent control policy by monitoring energy states in each component or the whole system is efficient for power saving in server systems whose system state, such as transaction request, can be completely observed. In this paper, we consider an optimal power-aware design in a cluster system and formulate the DPM problem by means of the Markov decision process. We derive the dynamic programming equation for the optimal control policy, which maximizes the expected reward per unit electrical power, which is called the power effectiveness, and give the policy iteration algorithm to determine the optimal control policy sequentially. In numerical experiments, we show the optimal control policy for an example of a cluster system with two service nodes, where the arrival stream of the transaction request is described as a Markov modulated Poisson process. In addition, based on the access data of an enterprise system, the optimal power-aware control for the cluster system and its effectiveness is examined.

Business Process and Practice Alignment Meta-model

Abstract Business Process Modelling (BPM) is one of the most important phases of information system design. Business Process meta-models allow capturing informational and behavioural aspects of business processes. Unfortunately, standard business process meta-modelling approaches, such as the Business Process Model and Notation (BPMN) Meta-model, Quality-Oriented Business Process Meta-Model (QOBPM) and Transactional Meta-Model for Business Process (TMBP) focus just on process description, providing different business process models. According to these meta-modelling approaches, it is not possible to compare and identify related daily practices in order to improve business process models. This lack of information recognizes that further research in Business Process (BP) meta-model is needed to reflect the evolution/change on software processes. Considering this limitation in BP meta-modelling, this paper presents a comparative study of the most recognized business process meta-models approaches and introduces a new BP meta-model designed by Business Process and Practice Alignment Meta-model (BPPAMeta-model). Our intention is to present observed problems in existing approaches and propose a business process meta-model that addresses features related to the alignment between daily work practices and business process descriptions.

Integrated Matrix-based Fault Tree Generation and Evaluation

Increasing complexity of products and safety regulations combined with an increasing amount of variants complicates the process of safety analysis within systems engineering. Moreover, it is known that the early avoidance or prevention of failures saves costs and improves the quality. As methods of safety analysis, i.e. fault tree analyses require immense manual efforts and expert knowledge, the efficiency of these analyses has to be improved. Our paper thus presents an approach to generate and evaluate fault trees by the usage of matrix-based models. It is an approach tailored to the early phases of system design and provides a preliminary fault tree analysis. It automatically generates fault trees and evaluates them. Thus, it facilitates the efficient identification of safety critical elements and the assessment and comparison of alternative system architecture concepts. This paper provides a brief introduction to fault tree analysis and presents existing approaches to automate the generation or synthesis of fault trees. The limitations of these approaches during early stages of design are discussed and the need for a tailored approach is derived. The developed approach consists of four phases and six steps which each are explained in detail. The whole approach is validated within a small industrial case study and its benefits and limitations are discussed. The case study shows, that the approach successfully improves the efficiency of a preliminary fault tree analysis.

Smart Control of Air Climatization System in Function on the Values of Mean Local Radiant Temperature

The hygrothermal comfort indoor conditions are defined as: those environmental conditions in which an individual exposed, expresses a state of satisfaction. These conditions cannot always be achieved anywhere in an optimal way and economically; in some cases they can be obtained only in work environments specific areas. This could be explained because of air conditioning systems designing is generally performed both on the basis of the fundamental parameters' average values, such as temperature, velocity and relative humidity (Ta, va e φa) and derived parameters such as operating temperature and mean radiant one (Top eTmr). However, in some specific cases—large open-spaces or in case of radiating surfaces—the descriptors defining indoor comfort conditions, based on average values, do not provide the optimum values required during the air conditioning systems design phase. This is largely due to the variability of real environmental parameters values compared to the average ones taken as input in the calculation. The results obtained in previous scientific papers on the thermal comfort have been the driving element of this work. It offers a simple, original and clever way of thinking about the new domotic systems for air conditioning, based on the “local mean radiant temperature.” This is a very important parameter when one wants to analyze comfort in environments characterized by the presence of radiating surfaces, as will be seen hereinafter. In order to take into account the effects of radiative exchanges in the open-space workplace, where any occupant may find themselves in different temperature and humidity conditions, this paper proposes an action on the domotic climate control, with ducts and vents air distribution placed in different zones.Comparisons were performed between the parameters values representing the punctual thermal comfort, with the Predicted Mean Vote PMV, in an environment marked by radiating surfaces (i.e continuous glass) and calculated with the local radiant temperature suggested in previous works, with the corresponding values obtained always varying the air speed or the air temperature inflated from the air vents, in order to achieve the optimal comfort conditions.

Reliability for Drug Targeting In Cancer Treatment through Nanotechnology (A Psychometric Approach)

The primary focus of the nanotechnology therapeutic approaches has been on early disease detection, drug discovery and monitoring, controlled release of therapeutic agents, and targeted drug delivery. Targeted drug delivery system requires more research including statistical modeling to establish the reliability in success of drug targeting. This part of every nanotechnology therapeutic approach is especially fundamental for reaching stronger therapeutic effects with lower side effects. In practice, we may be unable to accurately assess our nanotechnology drug delivery system designs to improve the reliability. This is likely due to the lack of a unified definition of reliability in system design phase. For this shortcoming, we introduce the notion of reliability in this context. Our proposed notion of reliability is flexible in allowing a general method for determining dose level. We then describe a methodology that enables us to determine an optimal dose level to achieve certain reliability. Although, in this report we focus on a special nanotechnology drug delivery system for cancer therapy, i.e. folate-conjugated gold nanoparticles for transfer to over expressed-folate-receptor cancerous cells, our developed strategies can be applied to many other drug delivery systems as well.

Safety issues in PV systems: Design choices for a secure fault detection and for preventing fire risk

Photovoltaic systems have played a key role over the last decade in the evolution of the electricity sector. In terms of safety design, it’s important to consider that a PV plant constitutes a special system of generation, where the Direct Current (DC) presence results in changes to the technical rules. Moreover, if certain electrical faults occur, the plant is a possible source of fire. Choices regarding the grounding of the generator and its protection devices are fundamental for a design that evaluates fire risk. The subject of the article is the analysis of the relation between electrical phenomena in PV systems and the fire risk related to ensuring appropriate fault detection by the electrical protection system. A description of a grid-connected PV system is followed firstly by a comparison of the design solutions provided by International Standards, and secondly by an analysis of electrical phenomena which may trigger a fire. A study of two existing PV systems, where electrical faults have resulted in fires, is then presented. The study highlights the importance of checking all possible failure modes in a PV system design phase, to assess fire risk in advance. Some guidelines for the mitigation of electrical faults that may result in a fire are finally provided.

Towards a Complete Model for Software Component Deployment on Heterogeneous Platform

Abstract This report briefly describes an ongoing research related to optimization of allocating software components to heterogeneous computing platform (which includes CPU, GPU and FPGA). Research goal is also presented, along with current hot topics of the research area, related research teams, and finally results and contribution of my research. It involves mathematical modelling which results in goal function, optimization method which finds a suboptimal solution to the goal function and a software modeling tool which enables graphical representation of the problem at hand and help developers determine component placement in the system design phase.

VLIV FORMÁTU UKLÁDANÝCH DOKUMENTŮ NA PRODUKTIVITU INFORMAČNÍCH SYSTÉMŮ

Document processing is significant and limiting factor of the efficiency of every information system that creates, stores, and revises documents during its operation. Selection of proper document format together with the data that describe the document can substantially influence the speed of processing the documents.We should consider the document format already in the phase of systems design. If documents that are processed are of one type it is useful to follow one descriptive style during their creation. This can be achieved through using sample document templates. Not less important is also the method of storing the documents. This aspect is crucial mainly in cases when the presentation and processing of the documents is fundamental. The design of the structure and methods of storing the documents are influenced by the operations that will be carried out with the docu­ments. Big impact on the structure has e.g. implementation of efficient searching algorithm in full text or semantic variant.This paper doesn‘t provide complex solution of document systems in information systems but uses suitable approaches and comparisons to show effective way how to implement such system with the compliance with new technologies.

Abstraction and approximation in fuzzy temporal logics and models

Abstract Recently, by defining suitable fuzzy temporal logics, temporal properties of dynamic systems are specified during model checking process, yet a few numbers of fuzzy temporal logics along with capable corresponding models are developed and used in system design phase, moreover in case of having a suitable model, it suffers from the lack of a capable model checking approach. Having to deal with uncertainty in model checking paradigm, this paper introduces a fuzzy Kripke model (FzKripke) and then provides a verification approach using a novel logic called Fuzzy Computation Tree Logic* (FzCTL*). Not only state space explosion is handled using well-known concepts like abstraction and bisimulation, but an approximation method is also devised as a novel technique to deal with this problem. Fuzzy program graph, a generalization of program graph and FzKripke, is also introduced in this paper in consideration of higher level abstraction in model construction. Eventually modeling, and verification of a multi-valued flip-flop is studied in order to demonstrate capabilities of the proposed models.

APLIKASI SISTEM INFORMASI PENJUALAN APOTEK

<p>Business management in the field of pharmacy requires a Sales Information database<br />systems. The purpose of this study is to design and apply the Sales Information System and to<br />identify the needs and requirements of the new system are made in order to improve the weakness<br />in the sales system. The method used is to make the sales information system design phases makes<br />flow diagram and context diagram. The results of the study were achieved is to produce a draft<br />Sales Information System that can find solutions quickly and effectively than the existing system<br />with a computerized system. Software used is by using Microsoft Visual Basic 6.</p>