This report is a thesis on requests from Sandvik Mining and Construction (SMC) in autumn of 2012. The goal of this work was to study the feasibility of creating and implementing an Equalized preventive maintenance program in SMC maintenance operations and reduce downtime for preventive maintenance (PM). To investigate whether this was possible, the authors studied the current procedures for the PM. The authors have collected and analyzed all relevant information within the maintenance department reporting system as well as through interviews determined whether it is practical to introduce a Equalized PM programs. The authors had also studied the possibilities to entrust part of the maintenance work to the operators of the machine cells. The results show that it is feasible to introduce an Equalized PM programs in operation when the PM is divided into smaller packets to reduce downtime at one time. Other benefits of the introduction of Equalized PM would be to increase the condition monitoring of components and systems.

Presently Sjöfartsverket do their maintenance according to a standard program, which means that every maintenance task will be done when the task limit occurs. This leads to a very long downtime for the aircraft in some occasions and very short downtime in others. The goal with this work is to reach a higher regularity of the aircraft operation. To reach a higher regularity for the operational needs, this work will present a hypothetic better maintenance concept for Swedish Maritime Administration. The concept is based on equalized maintenance structure, which means that every maintenance occasions are meant to take the same time to perform. This result will lead to easier planning and better maintenance overview of the aircraft operation. Different types of results have been presented depending on the size of the check cycle or if the engineering unit at the helicopter organization is going to use a reliability program in the future or not. Two with different types of check cycles and one, which can be considered as a future goal when a potential reliability program is in use.     The work of the equalized maintenance structure takes airworthiness limitation tasks in consideration and put them as “drop outs” besides the check cycle itself because of the high criticality in those items. Excel has been used to store and sort all the maintenance tasks, which are considered in this work, and pivot tables have been used to get an overview of the number of tasks in each interval. An aircraft reliability program has been suggested in the future due to the changes in escalation of intervals gives Sjöfartsverket the opportunity to optimize their equalized structure even further with less reduction of task intervals, a better task spread out and higher operational safety.

In this thesis, a 6-beam combiner using multiplexed holograms in dye-doped polymer is investigated. It is realized by recording six superimposed holographic gratings, which show uniform diffraction efficiency. The coupled wave theory for N superimposed gratings is more generalized and is used to analyze the amplitudes of diffracted waves in three different boundary conditions. Multiple-ring diffracted beam analysis is proposed to determine the dynamic range of a holographic material. The M/# is evaluated by recording a single hologram and counting the number of ring patterns in the diffracted beam. This analysis is extended to assess the equalized grating strength of N superimposed holograms. Six holograms with the equalized grating strength which can be assigned within the dynamic range of our material and show maximum diffraction efficiency are recorded. The phase locking of five beams to one reference beam is performed using PZT controller. The designs of lock-in amplifier, ramp generator and servo using commercial chips are demonstrated. The readout set-up used to split one single beam into six coherent copies is presented. The function of each part of the PZT controller in the readout set-up is discussed in detail. The intensity profile of an N-beam combiner is investigated by varying the phase angle between adjacent input waves. The entire solution which describes the amplitude of a combined beam is derived from generalized coupled wave theory. A simplified experimental set-up without a complicated PZT controller is demonstrated using a planoconvex lens. In order to provide six coherent light sources in future work, the injection locking of a single laser diode to the master laser diode is performed. An expected read-out setup is proposed to carry out both the achievement of six coherent sources and a 6 beam combination.

Most of PDE-based restoration models and their numerical realizations show a common drawback: loss of fine structures. In particular, they often introduce an unnecessary numerical dissipation on regions where the image content changes rapidly such as on edges and textures. This thesis studies the magnitude data/imagery of magnetic resonance imaging (MRI) which follows Rician distribution. It analyzes statistically that the noise in the magnitude MRI data is approximately Gaussian of mean zero and of the same variance as in the frequency-domain measurements. Based on the analysis, we introduce a novel partial differential equation (PDE)-based denoising model which can restore fine structures satisfactorily and simultaneously sharpen edges as needed. For an efficient simulation we adopt an incomplete Crank-Nicolson (CN) time-stepping procedure along with the alternating direction implicit (ADI) method. The algorithm is analyzed for stability. It has been numerically verified that the new model can reduce the noise satisfactorily, outperforming the conventional PDE-based restoration models in 3-4 alternating direction iterations, with the residual (the difference between the original image and the restored image) being nearly edgeree. It has also been verified that the model can perform edge-enhancement effectively during the denoising of the magnitude MRI imagery. Numerical examples are provided to support the claim.

Network lifetime is a key issue in wireless sensor networks where sensor nodes, distributed typically in remote/hostile sensing areas, are powered by finite energy batteries which are not easily replaced/recharged. Depletion of these finite energy batteries can result in a change in network topology or in the end of network life itself. Hence, prolonging the life of wireless sensor networks is important. Energy consumed in wireless sensor nodes can be for the purpose of i) sensing functions, ii) processing/computing functions, and ii) communication functions. For example, energy consumed by the transmit and receive electronics constitute the energy expended for communication functions. Our focus in this thesis is on the efficient use of energy for sensing. In particular, we are concerned with energy efficient algorithms for scheduling the sensing activity of sensor nodes. By scheduling the sensing activity we mean when to activate a sensor node for sensing (active mode) and when to keep it idle (sleep mode). The novel approach we adopt in this thesis to achieve efficient scheduling of sensing activity is an information coverage approach, rather than the widely adopted physical coverage approach. In the physical coverage approach, a point is said to be covered by a sensor node if that point lies within the physical coverage range (or the sensing radius) of that sensor, which is the maximum distance between the sensor and the point up to which the sensor can sense with acceptable accuracy. Information coverage, on the other hand, exploits cooperation among multiple sensors to accurately sense a point even if that point falls outside the physical coverage range of all the sensors. In this thesis, we address the question of how to schedule the activity of various sensor nodes in the network to enhance network lifetime using information coverage. In the first part of the thesis, we are concerned with scheduling of sensor nodes for sensing point targets using information coverage – example of a point-target being temperature or radiation level at a source or point that needs to be monitored. Defining a set of sensor nodes which collectively can sense a point-target accurately as an information cover, we propose an algorithm to obtain Disjoint Set of Information Covers (DSIC) that can sense multiple point-targets in a given sensing area. Being disjoint, the resulting information covers in the proposed algorithm allow a simple round-robin schedule of sensor activation (i.e., activate the covers sequentially). We show that the covers obtained using the proposed DSIC algorithm achieve longer network life compared to the covers obtained using an Exhaustive-Greedy-Equalized Heuristic (EGEH) proposed recently in the literature. We also present a detailed complexity comparison between the DSIC and EGEH algorithms. In the second part of the thesis, we extend the point target sensing problem in the first part to a full area sensing problem, where we are concerned with energy efficient ‘area-monitoring’ using information coverage. We refer to any set of sensors that can collectively sense all points in the entire area-to-monitor as a full area information cover. We first propose a low-complexity heuristic algorithm to obtain full area information covers. Using these covers, we then obtain the optimum schedule for activating the sensing activity of various sensors that maximizes the sensing lifetime. The optimum schedules obtained using the proposed algorithm is shown to achieve significantly longer sensing lifetimes compared to those achieved using physical coverage. Relaxing the full area coverage requirement to a partial area coverage requirement (e.g., 95% of area coverage as adequate instead of 100% area coverage) further enhances the lifetime. The algorithms proposed for the point targets and full area sensing problems in the first two parts are essentially centralized algorithms. Decentralized algorithms are preferred in large networks. Accordingly, in the last part of the thesis, we propose a low-complexity, distributed sensor scheduling algorithm for full area sensing using information coverage. This distributed algorithm is shown to result in significantly longer sensing lifetimes compared to those achieved using physical coverage.

För att vatten ska kunna levereras enligt de krav som ställs från användarna i samhället behövs ett väl anpassat ledningsnät. Det innebär bland annat att vatten ska finnas tillgängligt i den mängd som behövs och vid den tidpunkt som vatten krävs. För att vattenreningsverken ska kunna leverera rätt mängd vatten måste ledningsnätet vara dimensionerat för att kunna transportera allt vatten som skall pumpas ut till användarna. Detta kräver en god uppskattning om de vattenflöden som behövs. Det förväntade vattenflödet till olika samhällsanvändare uppskattas utifrån befintliga användningsmönster samt publikation P83, framtagen av Svenskt Vatten. Allt eftersom samhället utvecklas behöver publikationen uppdateras för att denna ska stämma så väl överens med verkligheten som möjligt. Vattenanvändningsmönster i skolor, kontor, handelsområden och industrier undersöktes som en del av ett pågående projekt för att undersöka om P83 bör uppdateras. För dessa har år- och dygnsvariationer, flöden och maxfaktorer analyserats från årslånga mätserier. Utifrån uppmätta värden kunde alternativa fördelningsnycklar som potentiellt skulle bidra till förbättring också analyseras. Resultaten tyder på att det finns förbättringsmöjligheter för flödesberäkningar för brukartyperna skolor, handel och industri jämfört med dagens metoder. För skolor och handel skulle inomhusarea vara en relevant fördelningsnyckel att använda vid beräkningar medan takyta vore en mer lämplig parameter att använda för industrier. De maxfaktorer som finns angivna i P83 stämde inte särskilt väl överens med de uppmätta i studien och skulle behöva uppdateras. Studien visar också på ett behov av att dela upp de brukarkategorier som finns i dagsläget till fler kategorier då de tre som finns i dagsläget är mycket generella. Dessutom undersöktes möjligheten att kombinera olika brukartyper för att utjämna vattenflöden under dygnet. Villor eller radhus bör lämpligen kombineras med skolor, kontor eller industrier för att få ett jämnare vattenflöde under dagtid. / For water to be delivered according to the requirements of the users in the society there is a need for the water pipelines to be well dimensioned. This means that the amount of water that is needed has to be available at the time when it is required. For the water treatment plants to be able to deliver the right amount of water the pipelines must be sized to carry the water that should be delivered to the users. This requires a good estimate of the amount of water needed. The expected water flow to different users is estimated based on existing water usage patterns as well as the P83 publication, developed by Swedish Water. As society develops the publication may need to be updated to correspond well with reality. Water use patterns in schools, offices, retail stores and industries were examined as a part of an ongoing project to investigate whether P83 should be updated. For these annual and diurnal variations, water flows and max factors were analyzed from yearlong series of measurements. Based on the measured values alternate allocation keys that could potentially contribute to improvement were analyzed. The results suggest that there are possible improvements for flow calculations for schools, retail stores and industry compared to current methods. For schools and retail stores the indoor area would be a relevant variable to use for calculations, while the roof area would be a more appropriate variable to use for industries. The max factors listed in P83 did not agree with those measured in the study and would need to be updated. The study shows that the three categories used in P83 are very general and ought to be divided into more specific categories. Furthermore, the possibility to combine different types of water users to equalize the water flow to an area during the day was analyzed. Villas or semi-attached houses should preferably be combined with schools, offices or industries for evening out the flow during day time.