A simulation model of the optimal maintenance strategy: conceptual agent-based approach

In this Master’s thesis agent-based modeling has been used to analyze maintenance strategy related phenomena. The main research question that has been answered was: what does the agent-based model made for this study tell us about how different maintenance strategy decisions affect profitability of equipment owners and maintenance service providers? Thus, the main outcome of this study is an analysis of how profitability can be increased in industrial maintenance context. To answer that question, first, a literature review of maintenance strategy, agent-based modeling and maintenance modeling and optimization was conducted. This review provided the basis for making the agent-based model. Making the model followed a standard simulation modeling procedure. With the simulation results from the agent-based model the research question was answered. Specifically, the results of the modeling and this study are: (1) optimizing the point in which a machine is maintained increases profitability for the owner of the machine and also the maintainer with certain conditions; (2) time-based pricing of maintenance services leads to a zero-sum game between the parties; (3) value-based pricing of maintenance services leads to a win-win game between the parties, if the owners of the machines share a substantial amount of their value to the maintainers; and (4) error in machine condition measurement is a critical parameter to optimizing maintenance strategy, and there is real systemic value in having more accurate machine condition measurement systems.

Evaluation of cardiopulmonary parameters and recovery from anesthesia in cougars (Puma concolor) anesthetized with detomidine/ketamine and isoflurane or sevoflurane

Abstract: The aim of this study was to assess the cardiopulmonary effects, the onset time after the administration of a detomidine/ketamine combination, and the recovery from anesthesia of cougars (Puma concolor) anesthetized with detomidine/ketamine and isoflurane or sevoflurane for abdominal ultrasound imaging. Fourteen animals were randomly allocated into two experimental groups: GISO (n=7) and GSEVO (n=7). Chemical restraint was performed using 0.15mg/kg detomidine combined with 5mg/kg ketamine intramuscularly; anesthesia induction was achieved using 2mg/kg propofol intravenously and maintenance with isoflurane (GISO) or sevoflurane (GSEVO). The following parameters were assessed: heart rate, respiratory rate, systolic and diastolic arterial blood pressure, mean arterial blood pressure, oxyhemoglobin saturation, rectal temperature, central venous pressure, and end-tidal carbon dioxide. The time to sternal recumbency (TSR) and time to standing position (TSP) were also determined. There was not statistically significant difference for the cardiopulmonary variables or TSP whereas TSR was significantly shorter in GSEVO. The time to onset of anesthesia was 11.1±1.2 minutes and 11.3±1.8 minutes for GISO and GSEVO, respectively. The anesthesia of cougars with detomidine/ketamine and isoflurane or sevoflurane was conducted with safety, cardiopulmonary stability, and increased time to sternal recumbency in the GISO group.

Maintenance of Brazilian Biodiversity by germplasm bank

Abstract: Currently the importance of using alternative strategies for biodiversity conservation is emphasized and since the establishment of germplasm bank is an alternative to the conservation of endangered species. This is a technique of great importance for the maintenance of Brazilian fauna. Since the early70'sthere was a growing concern about the need to preserve essential genetic resources for food and agriculture, mainly for conservation of genetic material from farm animals. Thus was created the Brasilia Zoo, in July 2010, the first Germplasm Bank of Wild Animals in Latin America, as an alternative strategy for the conservation of threatened or endangered species, using both gametes and somatic cells and stem cells. Then we argue to create new banks or research networks among different regions with aimed to tissue preservation.

Estimation of aircraft aerodynamic derivatives using Extended Kalman Filter

Design of flight control laws, verification of performance predictions, and the implementation of flight simulations are tasks that require a mathematical model of the aircraft dynamics. The dynamical models are characterized by coefficients (aerodynamic derivatives) whose values must be determined from flight tests. This work outlines the use of the Extended Kalman Filter (EKF) in obtaining the aerodynamic derivatives of an aircraft. The EKF shows several advantages over the more traditional least-square method (LS). Among these the most important are: there are no restrictions on linearity or in the form which the parameters appears in the mathematical model describing the system, and it is not required that these parameters be time invariant. The EKF uses the statistical properties of the process and the observation noise, to produce estimates based on the mean square error of the estimates themselves. Differently, the LS minimizes a cost function based on the plant output behavior. Results for the estimation of some longitudinal aerodynamic derivatives from simulated data are presented.

Characterization of Lubricating Oil Using Ultrasound

This paper presents an ultrasonic method to measure small concentrations of water in lubricating oil. It uses an ultrasonic measurement cell composed by a piezoceramic emitter (5 and 10 MHz), and a large aperture PVDF receiver that eliminates diffraction effects. The propagation velocity, attenuation coefficient and density of several samples of water-in-oil emulsion were measured. The concentrations of water of the samples were in the range of 0 to 5% in volume, and the results showed that these low concentrations can be discriminated within a resolution of 0.2% in the studied range, using the measurement of the propagation velocity.

Modelling flexible asset management in industrial maintenance companies and networks

The tightening competition and increasing dynamism have created an emerging need for flexible asset management. This means that the changes of market demand should be responded to with adjustments in the amount of assets tied to the balance sheets of companies. On the other hand, industrial maintenance has recently experienced drastic changes, which have led to an increase in the number of maintenance networks (consisting of customer companies that buy maintenance services, as well as various supplier companies) and inter-organizational partnerships. However, the research on maintenance networks has not followed the changes in the industry. Instead, there is a growing need for new ways of collaboration between partnering companies to enhance the competitiveness of the whole maintenance network. In addition, it is more and more common for companies to pursue lean operations in their businesses. This thesis shows how flexible asset management can increase the profitability of maintenance companies and networks under dynamic operating conditions, and how the additional value can then be shared between the network partners. Firstly, I have conducted a systematic literature review to identify what kind of requirements for asset management models are set by the increasing dynamism. Then I have responded to these requirements by constructing an analytical model for flexible asset management, linking asset management to the profitability and financial state of a company. The thesis uses the model to show how flexible asset management can increase profitability in maintenance companies and networks, and how the created value can be shared in the networks to reach a win-win situation. The research indicates that the existing models for asset management are heterogeneous by nature due to the various definitions of ‘asset management’. I conclude that there is a need for practical asset management models which address assets comprehensively with an inter-organizational, strategic view. The comprehensive perspective, taking all kinds of asset types into account, is needed to integrate the research on asset management with the strategic management of companies and networks. I will show that maintenance companies can improve their profitability by increasing the flexibility of their assets. In maintenance networks, reorganizing the ownership of the assets among the different network partners can create additional value. Finally, I will introduce flexible asset management contracts for maintenance networks. These contracts address the value sharing related to reorganizing the ownership of assets according to the principles of win-win situations.

Creating an open-books implementation framework for a maintenance-related value-based life-cycle model

This study is a qualitative action research by its nature with elements of personal design in the form of a tangible model implementation framework construction. Utilized empirical data has been gathered via two questionnaires in relation to the arranged four workshop events with twelve individual participants. Five of them represented maintenance customers, three maintenance service providers and four equipment providers respectively. Further, there are two main research objectives in proportion to the two complementary focusing areas of this thesis. Firstly, the value-based life-cycle model, which first version has already been developed prior to this thesis, requires updating in order to increase its real-life applicability as an inter-firm decision-making tool in industrial maintenance. This first research objective is fulfilled by improving appearance, intelligibility and usability of the above-mentioned model. In addition, certain new features are also added. The workshop participants from the collaborating companies were reasonably pleased with made changes, although further attention will be required in future on the model’s intelligibility in particular as main results, charts and values were all reckoned as slightly hard to understand. Moreover, upgraded model’s appearance and added new features satisfied them the most. Secondly and more importantly, the premises of the model’s possible inter-firm implementation process need to be considered. This second research objective is delivered in two consecutive steps. At first, a bipartite open-books supported implementation framework is created and its different characteristics discussed in theory. Afterwards, the prerequisites and the pitfalls of increasing inter-organizational information transparency are studied in empirical context. One of the main findings was that the organizations are not yet prepared for network-wide information disclosure as dyadic collaboration was favored instead. However, they would be willing to share information bilaterally at least. Another major result was that the present state of companies’ cost accounting systems will definitely need implementation-wise enhancing in future since accurate and sufficiently detailed maintenance data is not available. Further, it will also be crucial to create supporting and mutually agreed network infrastructure. There are hardly any collaborative models, methods or tools currently in usage. Lastly, the essential questions about mutual trust and predominant purchasing strategies are cooperation-wise important. If inter-organizational activities are expanded, a more relational approach should be favored in this regard. Mutual trust was also recognized as a significant cooperation factor, but it is hard to measure in reality.

Customer knowledge processing in maintenance business: case study

The purpose of the study is to examine and increase knowledge on customer knowledge processing in B2B context from sales perspective. Further objectives include identifying possible inhibiting and enabling factors in each phase of the process. The theoretical framework is based on customer knowledge management literature. The study is a qualitative study, in which the research method utilized is a case study. The empirical part was implemented in a case company by conducting in-depth interviews with the company’s value-selling champions located internationally. Context was maintenance business. Altogether 17 interviews were conducted. The empirical findings indicate that customer knowledge processing has not been clearly defined within the maintenance business line. Main inhibiting factors in acquiring customer knowledge are lack of time and vast amount of customer knowledge received. Enabling factors recognized are good customer relationships and sales representatives’ communication skills. Internal dissemination of knowledge is mainly inhibited by lack of time and restrictions in customer relationship management systems. Enabling factors are composition of the sales team and updated customer knowledge. Inhibiting utilization is lack of goals to utilize the customer knowledge and a low quality of the knowledge. Moreover, customer knowledge is not systematically updated nor analysed. Management of customer knowledge is based on the CRM system. As implications of the study, it is suggested for the case company to define customer knowledge processing in order to support maintenance business process.

Supplier Delivery Quality Evaluation in Maintenance Supporting Spare Part Business

The focus of this thesis is the issues related to the operational purchasing level supply chain process. Due to this limitation, the physical product quality issues do not belong to the primary concerns of this thesis, whereas the bilateral processes between the supplier and the purchasing organizations are of interest. Also, the issues related to the delivery timing are excluded from the study. Because the perspective is on the issues involved in the supply chain operations, the bilateral communication issues between supplier representative and purchaser are also considered.

Modelling of ultrasound assisted mixing in Newtonian and non-Newtonian liquids

The purpose of this work is to obtain a better understanding of behaviour of possible ultrasound appliance on fluid media mixing. The research is done in the regard to Newtonian and non-Newtonian fluids. The process of ultrasound appliance on liquids is modelled in COMSOL Multiphysics software. The influence of ultrasound using is introduced as waveform equation. Turbulence modelling is fulfilled by the k-ε model in Newtonian fluid. The modeling of ultrasound assisted mixing in non-Newtonian fluids is based on the power law. To verify modelling results two practical methods are used: Particle Image Velocimetry and measurements of mixing time. Particle Image Velocimetry allows capturing of velocity flow field continuously and presents detailed depiction of liquid dynamics. The second way of verification is the comparison of mixing time of homogeneity. Experimentally achievement of mixing time is done by conductivity measurements. In modelling part mixing time is achieved by special module of COMSOL Multiphysics – the transport of diluted species. Both practical and modelling parts show similar radial mechanism of fluid flow under ultrasound appliance – from the horn tip fluid moves to the bottom and along the walls goes back. Velocity profiles are similar in modelling and experimental part in the case of Newtonian fluid. In the case of non-Newtonian fluid velocity profiles do not agree. The development track of ultrasound-assisted mixing modelling is presented in the thesis.

Evidencing and Sharing Value with Decision Making Models in an Industrial Maintenance Network

The objective of this thesis is to concretize the potential benefits that the industrial maintenance case network could achieve through using the value-based life-cycle model and the flexible asset management model. It is also inspected what factors prevent value creation and sharing in the maintenance contract practices of the case network. This thesis is a case study which utilizes modelling. Four scenarios were developed to demonstrate value creation in the future. The data was partly provided by the collaborating company, partly gathered from public financial statement information. The results indicate that value has been created through the past maintenance of the collaborating company’s rod mill and that profitability of the collaborating company has been mostly on satisfactory level during the past few years. Potential value might be created by increasing the share of proactive maintenance of the rod mill in the future. Profitability of the network could be improved in the future through flexible asset management operations. The main obstacle for value creation and sharing seems to be the lack of sufficient trust between the network members.

Intima-media thickness evaluation by B-mode ultrasound: Correlation with blood pressure levels and cardiac structures

The aim of this study was to analyze the thickness of the intima-media complex (IMC) using a noninvasive method. The carotid and femoral common arteries were evaluated by noninvasive B-mode ultrasound in 63 normotensive and in 52 hypertensive subjects and the thickness of the IMC was tested for correlation with blood pressure, cardiac structures and several clinical and biological parameters. The IMC was thicker in hypertensive than in normotensive subjects (0.67 ± 0.13 and 0.62 ± 0.16 vs 0.54 ± 0.09 and 0.52 ± 0.11 mm, respectively, P<0.0001). In normotensive patients, the simple linear regression showed significant correlations between IMC and age, body mass index and 24-h systolic blood pressure for both the carotid and femoral arteries. In hypertensives the carotid IMC was correlated with age and 24-h systolic blood pressure while femoral IMC was correlated only with 24-h diastolic blood pressure. Forward stepwise regression showed that age, body mass index and 24-h systolic blood pressure influenced the carotid IMC relationship (r2 = 0.39) in normotensives. On the other hand, the femoral IMC relationship was influenced by 24-h systolic blood pressure and age (r2 = 0.40). In hypertensives, age and 24-h systolic blood pressure were the most important determinants of carotid IMC (r2 = 0.37), while femoral IMC was influenced only by 24-h diastolic blood pressure (r2 = 0.10). There was an association between carotid IMC and echocardiographic findings in normotensives, while in hypertensives only the left posterior wall and interventricular septum were associated with femoral IMC. We conclude that age and blood pressure influence the intima-media thickness, while echocardiographic changes are associated with the IMC.

Effect of saline infusion for the maintenance of blood volume on pulmonary gas exchange during temporary abdominal aortic occlusion

We analyzed the effects of saline infusion for the maintenance of blood volume on pulmonary gas exchange in ischemia-reperfusion syndrome during temporary abdominal aortic occlusion in dogs. We studied 20 adult mongrel dogs weighing 12 to 23 kg divided into two groups: ischemia-reperfusion group (IRG, N = 10) and IRG submitted to saline infusion for the maintenance of mean pulmonary arterial wedge pressure between 10 and 20 mmHg (IRG-SS, N = 10). All animals were anesthetized and maintained on spontaneous ventilation. After obtaining baseline measurements, occlusion of the supraceliac aorta was performed by the inflation of a Fogarty catheter. After 60 min of ischemia, the balloon was deflated and the animals were observed for another 60 min of reperfusion. The measurements were made at 10 and 45 min of ischemia, and 5, 30, and 60 min of reperfusion. Pulmonary gas exchange was impaired in the IRG-SS group as demonstrated by the increase of the alveolar-arterial oxygen difference (21 ± 14 in IRG-SS vs 11 ± 8 in IRG after 60 min of reperfusion, P = 0.004 in IRG-SS in relation to baseline values) and the decrease of oxygen partial pressure in arterial blood (58 ± 15 in IRG-SS vs 76 ± 15 in IRG after 60 min of reperfusion, P = 0.001 in IRG-SS in relation to baseline values), which was correlated with the highest degree of pulmonary edema in morphometric analysis (0.16 ± 0.06 in IRG-SS vs 0.09 ± 0.04 in IRG, P = 0.03 between groups). There was also a smaller ventilatory compensation of metabolic acidosis after the reperfusion. We conclude that infusion of normal saline worsened the gas exchange induced by pulmonary reperfusion injury in this experimental model.

Aircraft tracking and classification with vhf passive bistatic radar

Since the times preceding the Second World War the subject of aircraft tracking has been a core interest to both military and non-military aviation. During subsequent years both technology and configuration of the radars allowed the users to deploy it in numerous fields, such as over-the-horizon radar, ballistic missile early warning systems or forward scatter fences. The latter one was arranged in a bistatic configuration. The bistatic radar has continuously re-emerged over the last eighty years for its intriguing capabilities and challenging configuration and formulation. The bistatic radar arrangement is used as the basis of all the analyzes presented in this work. The aircraft tracking method of VHF Doppler-only information, developed in the first part of this study, is solely based on Doppler frequency readings in relation to time instances of their appearance. The corresponding inverse problem is solved by utilising a multistatic radar scenario with two receivers and one transmitter and using their frequency readings as a base for aircraft trajectory estimation. The quality of the resulting trajectory is then compared with ground-truth information based on ADS-B data. The second part of the study deals with the developement of a method for instantaneous Doppler curve extraction from within a VHF time-frequency representation of the transmitted signal, with a three receivers and one transmitter configuration, based on a priori knowledge of the probability density function of the first order derivative of the Doppler shift, and on a system of blocks for identifying, classifying and predicting the Doppler signal. The extraction capabilities of this set-up are tested with a recorded TV signal and simulated synthetic spectrograms. Further analyzes are devoted to more comprehensive testing of the capabilities of the extraction method. Besides testing the method, the classification of aircraft is performed on the extracted Bistatic Radar Cross Section profiles and the correlation between them for different types of aircraft. In order to properly estimate the profiles, the ADS-B aircraft location information is adjusted based on extracted Doppler frequency and then used for Bistatic Radar Cross Section estimation. The classification is based on seven types of aircraft grouped by their size into three classes.