2,791 research outputs found

    Graph-Search and Differential Equations for Time-Optimal Vessel Route Planning in Dynamic Ocean Waves

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    Time-optimal paths are evaluated by VISIR (\u201cdis- coVerIng Safe and effIcient Routes\u201d), a graph-search ship routing model, with respect to the solution of the fundamental differential equations governing optimal paths in a dynamic wind-wave environment. The evaluation exercise makes use of identical setups: topological constraints, dynamic wave environmental conditions, and vessel-ocean parametrizations, while advection by external currents is not considered. The emphasis is on predicting the time-optimal ship headings and Speeds Through Water constrained by dynamic ocean wave fields. VISIR upgrades regarding angular resolution, time-interpolation, and static nav- igational safety constraints are introduced. The deviations of the graph-search results relative to the solution of the exact differential equations in both the path duration and length are assessed. They are found to be of the order of the discretization errors, with VISIR\u2019s solution converging to that of the differential equation for sufficient resolution

    Simulating interbank payment and securities settlement mechanisms with the BoF-PSS2 simulator

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    The simulation technique provides a new means for analysing complex interdependencies in payment and securities settlement processing. The Bank of Finland has developed a payment and settlement system simulator (BoF-PSS2) that can be used for constructing simulation models of payment and securities settlement systems. This paper describes the main elements of payment and settlement systems (system structures, interdependencies, processing steps, liquidity consumption, cost and risk dimensions) and how these can be treated in simulation studies. It gives also examples on how these elements have been incorporated in the simulator, as well as an overview of the structure and the features of the BoF-PSS2 simulator.simulations; simulator; payment systems; clearing/settlement; liquidity

    A Priority-based Fair Queuing (PFQ) Model for Wireless Healthcare System

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    Healthcare is a very active research area, primarily due to the increase in the elderly population that leads to increasing number of emergency situations that require urgent actions. In recent years some of wireless networked medical devices were equipped with different sensors to measure and report on vital signs of patient remotely. The most important sensors are Heart Beat Rate (ECG), Pressure and Glucose sensors. However, the strict requirements and real-time nature of medical applications dictate the extreme importance and need for appropriate Quality of Service (QoS), fast and accurate delivery of a patient’s measurements in reliable e-Health ecosystem. As the elderly age and older adult population is increasing (65 years and above) due to the advancement in medicine and medical care in the last two decades; high QoS and reliable e-health ecosystem has become a major challenge in Healthcare especially for patients who require continuous monitoring and attention. Nevertheless, predictions have indicated that elderly population will be approximately 2 billion in developing countries by 2050 where availability of medical staff shall be unable to cope with this growth and emergency cases that need immediate intervention. On the other side, limitations in communication networks capacity, congestions and the humongous increase of devices, applications and IOT using the available communication networks add extra layer of challenges on E-health ecosystem such as time constraints, quality of measurements and signals reaching healthcare centres. Hence this research has tackled the delay and jitter parameters in E-health M2M wireless communication and succeeded in reducing them in comparison to current available models. The novelty of this research has succeeded in developing a new Priority Queuing model ‘’Priority Based-Fair Queuing’’ (PFQ) where a new priority level and concept of ‘’Patient’s Health Record’’ (PHR) has been developed and integrated with the Priority Parameters (PP) values of each sensor to add a second level of priority. The results and data analysis performed on the PFQ model under different scenarios simulating real M2M E-health environment have revealed that the PFQ has outperformed the results obtained from simulating the widely used current models such as First in First Out (FIFO) and Weight Fair Queuing (WFQ). PFQ model has improved transmission of ECG sensor data by decreasing delay and jitter in emergency cases by 83.32% and 75.88% respectively in comparison to FIFO and 46.65% and 60.13% with respect to WFQ model. Similarly, in pressure sensor the improvements were 82.41% and 71.5% and 68.43% and 73.36% in comparison to FIFO and WFQ respectively. Data transmission were also improved in the Glucose sensor by 80.85% and 64.7% and 92.1% and 83.17% in comparison to FIFO and WFQ respectively. However, non-emergency cases data transmission using PFQ model was negatively impacted and scored higher rates than FIFO and WFQ since PFQ tends to give higher priority to emergency cases. Thus, a derivative from the PFQ model has been developed to create a new version namely “Priority Based-Fair Queuing-Tolerated Delay” (PFQ-TD) to balance the data transmission between emergency and non-emergency cases where tolerated delay in emergency cases has been considered. PFQ-TD has succeeded in balancing fairly this issue and reducing the total average delay and jitter of emergency and non-emergency cases in all sensors and keep them within the acceptable allowable standards. PFQ-TD has improved the overall average delay and jitter in emergency and non-emergency cases among all sensors by 41% and 84% respectively in comparison to PFQ model

    Optimal path planning for autonomous underwater gliders in time-varying flow fields

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    University of Technology Sydney. Faculty of Engineering and Information Technology.Marine robots perform various oceanic missions for commercial, scientific and military purposes. Some of these tasks include resource tracking, environmental surveying and coastal surveillance. Underwater gliders are a special class of marine robots that do not use active propulsions to move forward. This property makes the gliders more energy-efficient compared to other marine robots, and thus well-suited for long-duration missions. These missions benefit from autonomous operations that are either energy-optimal or time-optimal to maximising glider operation time and minimise human interactions. Such a level of automation is difficult to achieve, however. The underwater glider operates under a high-dimensional dynamic model with non-linear control, making it difficult to model mathematically. Optimal navigation in a flow field environment, known as Zermelo's Problem, is also a century-old open problem. This research introduces a trim-based model that reduces the glider control problem to a simpler 6D kinodynamic problem. We address this simpler problem using a state-of-the-art sampling-based algorithm to demonstrate full 3D underwater glider motion planning over various static flow fields and obstacles. For real-world applications, it is also essential to consider the dynamics of the environment. Therefore it is natural to expect planning algorithms for underwater gliders to handle variations in flow fields. As the glider's performance heavily depends on the surrounding flow field, planning involves the time-dependent shortest path (TDSP) problem, which has been open since the original work on graph search problem in the 1960s. This research introduces a new special case of the TDSP problem for vehicles in dynamic ocean currents. An optimal policy is solved for a time-dependent discrete graph over a dynamic flow field in polynomial time. Integrating both the trim-based and TDSP work addresses the path planning problem for underwater gliders by synthesising a continuous path from the optimal policy using the trim-based model. The significance of this research is that it introduces an increased level of autonomy in underwater robots. The theoretical work allows for more accurate glider navigation, and considering dynamic ocean currents allows the glider to exploit the environment for practical advantages. These results also improve autonomous operation so that it requires less manual intervention from humans. This thesis shows examples of these ideas, and we are currently planning a long-duration field deployment to demonstrate these results in practice

    Machinery management in bio-production systems: planning and scheduling aspects

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     D. D. Bochtis(Department of Biosystems Engineering, Faculty of Agricultural Sciences, University of Aarhus, Blichers Alle´ 20, P.O. box 50, Greece) Abstract: Most operations in bio-production systems involve a number of highly interconnected tasks executed by co-operating machinery systems operating in series or in parallel.  An envisioned future team of identical field-robots could represent an example of the former case, while machinery systems including a number of primary units supported by a number of service (mainly transport) units involved in “output material flow” operations, such as harvesting, as well as in “input material flow” operations, such as spraying and fertilising, could represent examples of the later. the efficient execution of such operations requires considerable efforts in terms of scheduling and planning.  Here, a classification scheme for the management task of planning and scheduling for bio-production machinery systems is proposed, as a first step towards implementing appropriate management tools used in industrial management domain.  The identifications of the characteristics of the decision problems related to the management of these systems can provide the basis for their mapping to the appropriate operational research approaches.Keywords: agricultural machinery management, field logistics, B-patterns, biomass supply chain, farm management, farm machinery Citation: Bochtis D D.  Machinery management in bio-production systems: Planning and scheduling aspects.  Agric Eng Int: CIGR Journal, 2010, 12(2): 55-63. &nbsp

    Analysis, Design, and Implementation of a training center for variable-speed drive assembly production : Case ABB Oy

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    In manufacturing constant developments in production, processes, and layouts are required to respond towards increased production volume, quality, and customer requirements while meeting production targets and objectives. The case company of this thesis is ABB Ltd Drives Manufacturing Unit, which specializes in variable-speed drive production. ABB has recognized the need for re-designing a new and effective training center that supports One-piece flow assembly production since the old model is based on a cell production method. The training center is used for the training and integration of the company's new and experienced assemblers. The aim of the research is to analyze the current training concept, design a new technical solution, and create a detailed implementation plan. Thus, the following research questions were developed: RQ1: How to develop and re-design a training center that supports the assembler for One-piece flow method production of variable-speed drives? RQ2: How to design and create the best possible layout and solution to guarantee safety, flexibility, ergonomics, clear flow, and the maximum utilization of space? RQ3: How to implement a training center that does not disrupt the main production lines and makes that way operations more efficient? To achieve the objectives, the waste, bottlenecks, and issues of the current design were first identified by observing the training process and organizing focus groups and workshops with the production line and logistics (customer), and with the project team. Work-time studies were also conducted to solve the flow, outputs, cycle time, and waste time of the current process. These data collection methods aided in identifying potential improvement opportunities for the new design. The layout design process was committed by utilizing Lean principles and the Systematic layout planning procedure. AutoCAD was used to create and map various layout structures, options, and alternatives. The design process required the tendering of two layout location options, which were solved using the quantitative multiple attribute decision-making method, Weighted decision matrix (WDM), with voting based on the scoring of various criteria and features. The result was a Flexible 6-phase U-model one-piece flow training center that allows assemblers to be trained in both one-piece flow and cell production methods. The new design's scope of work was delivered to the supplier, numerous negotiations were held to achieve the best final solution, and the new training center was ordered. In the end, a detailed implementation plan with an estimated schedule was created and a future action list was established. The new design fulfils the objectives and eliminates all issues, waste, and bottlenecks while also ensuring safety, ergonomics, flexibility, a clear flow, and a high-quality training process. With the new design, the efficiency, quality, and output of training and production operations will improve.Teollisuuden alalla tuotantojärjestelmiä, prosesseja ja layouteja on jatkuvasti kehitettävä sekä modifioitava reagoidakseen kasvaneisiin tuotantomääriin sekä laatu- ja asiakasvaatimuksiin ja saavuttaakseen asetetut tuotantotavoitteet ja päämäärät. Tämän opinnäytetyön toimeksiantaja on ABB Oy Drives Manufacturing -yksikkö, joka on erikoistunut taajuusmuuttajatuotantoon. Toimeksiantaja on tunnistanut tarpeen uuden ja tehokkaamman koulutuslinjan suunnitteluun One-piece flow malliseen taajuusmuuttajien kokoonpanotuotantoon, sillä vanha tuotantomalli perustuu solutuotantomenetelmään. Koulutuslinjaa käytetään niin uusien kuten jo talossa olevien vanhojen kokoonpanoasentajien koulutukseen ja integrointiin. Tutkimuksen tavoitteena on analysoida nykyinen koulutuskonsepti, suunnitella uusi tekninen ratkaisu ja laatia yksityiskohtainen implementointisuunnitelma. Tavoitteiden saavuttamista varten on kehitetty seuraavat kolme tutkimuskysymystä: RQ1: Kuinka kehittää ja suunnitella koulutuslinja, joka tukee asentajia One-piece flow malliseen kokoonpanotuotantoon? RQ2: Miten suunnitella ja luoda paras mahdollinen layout ja ratkaisu, joka takaa turvallisuuden, joustavuuden, ergonomian, selkeän virtauksen ja maksimaalisen tilankäytön? RQ3: Kuinka implementoida koulutuslinja, joka ei häiritse päätuotantolinjoja ja tehostaa siten operaatioiden tehokkuutta? Saavuttaakseen tavoitteet, nykyisen koulutuskonseptin aiheuttamat pullonkaulat, ongelmat ja hukka tunnistettiin ensin havainnoimalla koulutusprosessia ja järjestämällä haastatteluja sekä työpajoja tuotantolinjan ja logistiikan (asiakkaan) sekä projektiryhmän kanssa. Nykyisen prosessin virtauksen, ulostulon, tahti -ja hukka-ajan selvittämiseksi suoritettiin myös työaikatutkimuksia. Nämä tiedonkeruumenetelmät auttoivat kehitysmahdollisuuksien tunnistamisessa uutta ratkaisua varten. Layout suunnitteluprosessi toteutettiin Lean-periaatteita ja systemaattista layout suunnittelua käyttäen. AutoCAD layout suunnittelusovellusta käytettiin erilaisien asettelurakenteiden ja vaihtoehtojen luomiseen sekä kartoittamiseen. Suunnitteluprosessi edellytti kahden layout-sijaintivaihtoehdon kilpailuttamista. Lopputulos ratkaistiin äänestämällä kvantitatiivisen päätöksentekomatriisin (WDM) avulla, joka perustui eri kriteerien ja ominaisuuksien pisteytykseen. Tulokseksi saatiin joustava 6-vaiheinen U-mallinen One-piece flow koulutuslinja, jonka avulla asentajia voidaan kouluttaa sekä One-piece flow että solutuotantomallisesti. Uuden koulutuslinjan työn laajuus -dokumentti toimitettiin toimittajalle sekä lukuisia neuvotteluja käytiin parhaan loppuratkaisun saavuttamiseksi, jonka jälkeen uusi koulutuslinja tilattiin. Lopuksi koostettiin yksityiskohtainen implementointisuunnitelma arvioituineen aikatauluineen ja laadittiin toimenpidelista tulevaisuutta varten. Uusi ratkaisu täyttää asetetut tavoitteet ja eliminoi kaikki ongelmat, hukat ja pullonkaulat sekä takaa turvallisuuden, ergonomian, joustavuuden, selkeän virtauksen ja laadukkaan koulutusprosessin. Uuden ratkaisun myötä koulutuksen ja operaatioiden tehokkuus, laatu ja tuottavuus paranevat

    Dynamic scheduling in a multi-product manufacturing system

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    To remain competitive in global marketplace, manufacturing companies need to improve their operational practices. One of the methods to increase competitiveness in manufacturing is by implementing proper scheduling system. This is important to enable job orders to be completed on time, minimize waiting time and maximize utilization of equipment and machineries. The dynamics of real manufacturing system are very complex in nature. Schedules developed based on deterministic algorithms are unable to effectively deal with uncertainties in demand and capacity. Significant differences can be found between planned schedules and actual schedule implementation. This study attempted to develop a scheduling system that is able to react quickly and reliably for accommodating changes in product demand and manufacturing capacity. A case study, 6 by 6 job shop scheduling problem was adapted with uncertainty elements added to the data sets. A simulation model was designed and implemented using ARENA simulation package to generate various job shop scheduling scenarios. Their performances were evaluated using scheduling rules, namely, first-in-first-out (FIFO), earliest due date (EDD), and shortest processing time (SPT). An artificial neural network (ANN) model was developed and trained using various scheduling scenarios generated by ARENA simulation. The experimental results suggest that the ANN scheduling model can provided moderately reliable prediction results for limited scenarios when predicting the number completed jobs, maximum flowtime, average machine utilization, and average length of queue. This study has provided better understanding on the effects of changes in demand and capacity on the job shop schedules. Areas for further study includes: (i) Fine tune the proposed ANN scheduling model (ii) Consider more variety of job shop environment (iii) Incorporate an expert system for interpretation of results. The theoretical framework proposed in this study can be used as a basis for further investigation
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