22 May 2002
No description available.
A Metadata Inference Framework to Provide Operational Information Support for Fault Detection and Diagnosis Applications in Secondary HVAC SystemsGao, Jingkun 01 December 2017 (has links)
As the cost of hardware decreases and software technology advances, building automation systems (BAS) have been widely deployed to new buildings or as part of the retrofit to replace the old control systems. Though they are becoming more prevalent and promise important benefits to the society, such as improved energy-efficiency and occupants’ comfort, many of their benefits remain unreachable. Research suggests that this is because of the heterogeneous, fragmented and nonstandardized nature of existing BASs. One of the purported benefits of these systems is the ability to reduce energy consumption through the application of automated approaches such as fault detection and diagnosis (FDD) algorithms. Savings of up to 0.16 quadrillion BTUs per year could be obtained in the US alone through the use of these approaches, which are just software applications running on BAS hardware. However, deployment of these applications for buildings remains a challenge due to the non-trivial efforts of organizing, managing and extracting metadata associated with sensors (e.g., information about their type, function, etc.), which is required by them. One of the reasons leading to the problem is that varying conventions, acronyms, and standards are used to define this metadata. Though standards and governmentmandated policies may lift these obstacles and enable these softwarebased improvements to our building stock, this effort could take years to come to fruition and there are alternative technical solutions, such as automated metadata inference techniques, that could help reign in on the non-standardized nature of today’s BASs. This thesis sheds light on the visibility of this alternative approach by answering three key questions, which are then validated using data from more than 400 buildings in the US: (a) What is the specific operational information required by FDD approaches for secondary heating, ventilation, and air conditioning (HVAC) systems found in existing literature? (b) How is the performance of existing metadata inference approaches affected by changes in building characteristics, weather conditions, building usage patterns, and geographical locations? (c) What is an approach that can provide physical interpretations in the case of incorrect metadata being inferred? We find that: (a) The BAS points required by more than 30% of FDD approaches include six sensors in AHUs monitoring supply air temperature, outside air temperature, chilled water valve position, return air temperature, supply air flow rate, and mixed air temperature; (b) The average performance of existing inference approaches in terms of accuracy is similar across building sites, though there is significant variance, and the expected accuracy of classifying the type of points required by a particular FDD application for a new unseen building is, on average, 75%; (c) A new approach based on physical models is developed and validated on both the simulation data and the real-world data to infer the point types confused by data-driven models with an accuracy ranging from 73% to 100%, and this approach can provide physical interpretations in the case of incorrect inference. Our results provide a foundation and starting point to infer the metadata required by FDD approaches and minimize the implementation cost of deploying FDD applications on multiple buildings.
This thesis is a case study of CNDD-FDD, a former rebel group turned political party in Burundi. The analysis will take off in 1994 when the rebel group is established and concluded today in 2019 with CNDD-FDD being an increasingly authoritarian one-party ruler. This thesis adds to the recent resurgence of literature focused on ideology and how it is changed and reshaped in the post-conflict setting. The focus of the analysis is therefore how the ideology in CNDD-FDD changes over time. The analysis will use primary sources from the actor for capturing their ideology, together with secondary sources for creating context. The analysis uses a newly developed theoretical framework by Sindre (2018) consisting of two dimensions, a conflict cleavage dimension and a peacebuilding dimension, with the objective of capturing ideological change in CNDD-FDD as well as developing the framework. A negative shift on both dimensions are observed over time, and a new issue of openness is suggested to be added to the peacebuilding dimension.
05 August 2011
Long Term Evolution (LTE) developed by Third Generation Partnership Project (3GPP) is expected to be the standard of the Fourth-Generation (4G) of wireless communication system. LTE supports Frequency Division Duplex (FDD) and Time Division Duplex (TDD), and both of them are based on Orthogonal Frequency Division Multiplexing (OFDM) system in downlink. OFDM systems are sensitive to timing and frequency offset. Therefore, synchronization plays an important role in OFDM systems. In this thesis, we study synchronization problems of a LTE FDD baseband receiver. Particularly, we develop a complete procedure to deal with the synchronization problems. The basic design concept and procedure are as follows: The receiver estimates and compensates the timing and frequency offset by using the repetition property of the cyclic prefix. In the meanwhile, the receiver also detects cyclic prefix mode (or the length of the cyclic prefix). After the frequency offset has been compensated, the receiver then processes cell search. To this end, we multiply each subcarrier by the synchronization sequence provided by LTE specification and transform them into time domain. We then estimate the channel energy in time domain to detect the Cell Identity (Cell ID). Using computer simulations, we verify that the designed receiver performs well.
Signalakquisition in DS-Spreizspektrum-Systemen und ihre Anwendung auf den 3GPP-FDD-Mobilfunkstandard /Zoch, André. January 2004 (has links) (PDF)
Techn. Universiẗat, Diss--Dresden, 2004.
Signalakquisition in DS-Spreizspektrum-Systemen und ihre Anwendung auf den 3GPP-FDD-MobilfunkstandardZoch, André Unknown Date (has links) (PDF)
Techn. Universiẗat, Diss., 2004--Dresden.
Phan Huy, Dinh-Thuy
14 December 2015
Cette thèse étudie la technique dite de ‘Retournement Temporel’ afin d’améliorer l’efficacité énergétique des futurs réseaux mobiles d’une part, et réduire le coût des futurs terminaux mobiles, d’autre part. Le retournement temporel consiste à utiliser l’inverse temporel de la réponse impulsionnelle du canal de propagation entre un émetteur et un récepteur pour préfiltrer l’émission d’un signal de données. Avantageusement, le signal ainsi préfiltré est reçu avec une puissance renforcée (c’est la focalisation spatiale) et un écho principal qui est renforcé par rapport aux échos secondaires (c’est la compression temporelle). Lors d’une étape préalable d’apprentissage, l’émetteur estime le canal en mesurant un signal pilote provenant du récepteur. La focalisation spatiotemporelle n’est obtenue qu’à condition que la propagation demeure identique entre la phase d’apprentissage et la phase de transmission de données : c’est la condition de ‘réciprocité du canal’. De nombreux travaux montrent que la focalisation spatiale permet de réduire la puissance émise nécessaire pour atteindre une puissance cible au récepteur d’une part, et que la compression temporelle permet de réduire la complexité du récepteur nécessaire pour gérer l’effet des échos multiples, d’autre part. Cependant, les études sur la réduction de la complexité du récepteur se limitent à l’ultra large bande. Des travaux de cette thèse (basés sur des simulations et des mesures expérimentales) montrent que pour des bandes de fréquences plus typiques des futurs réseaux mobiles (fréquence porteuse à 1GHz et spectre de 30 MHz à 100 MHz), grâce au retournement temporel, un récepteur simple et un signal monoporteuse suffisent pour atteindre de hauts débits. En outre, la condition de réciprocité du canal n’est pas vérifiée dans deux scénarios typiques des réseaux mobiles. Tout d’abord, dans la plupart des réseaux mobiles européens, le mode de duplex en fréquence est utilisé. Ce mode implique que l’émetteur et le récepteur communiquent l’un avec l’autre sur des fréquences porteuses distinctes, et donc à travers des canaux de propagations différents. De plus, lorsqu’on considère un récepteur sur un véhicule connecté en mouvement, l’émetteur et le récepteur communiquent l’un avec l’autre à des instants distincts, correspondants à des positions distinctes du véhicule, et donc à travers des canaux de propagations différents. Des travaux de cette thèse proposent des solutions pour obtenir la focalisation spatio-temporelle dans ces deux scenarios. Enfin, des travaux de la thèse explorent la combinaison du retournement temporel avec d’autres techniques de traitement de signal récentes (la modulation spatiale, d’une part, et une nouvelle forme d’onde multiporteuse, d’autre part), ou des scenarios de déploiement nouveaux (ondes millimétriques et très grands réseaux d’antennes pour inter-connecter les noeuds d’un réseau ultra dense) ou de nouvelles applications (guidage et navigation) envisageables pour les futurs réseaux mobiles. / This thesis studies the time reversal technique to improve the energy efficiency of future mobile networks and reduce the cost of future mobile devices. Time reversal technique consists in using the time inverse of the propagation channel impulse response (between a transceiver and a receiver) as a prefilter. Such pre-filtered signal is received with a stronger power (this is spatial focusing) and with a strong main echo, relatively to secondary echoes (this is time compression). During a previous learning phase, the transceiver estimates the channel by measuring the pilot signal emitted by the receiver. Space-time focusing is obtained only at the condition that the propagation remains identical between the learning phase and the data transmission phase: this is the ‘channel reciprocity’ condition. Numerous works show that spatial focusing allows for the reduction of the required transmit power for a given target received power, on the one hand, and that time compression allow for the reduction of the required complexity at the receiver side to handle multiple echoes, on the other hand. However, studies on complexity reduction are limited to ultra wideband. Some works of this thesis (based on simulations and experimental measurements) show that, for bands which are more typical for future networks (a carrier frequency of 1GHz and a spectrum of 30 MHz to 100 MHz), thanks to time reversal, a simple receiver and a mono-carrier signal are sufficient to reach high data rates. Moreover, the channel reciprocity condition is not verified in two scenarios which are typical from mobile networks. Firstly, in most European mobile networks, the frequency division duplex mode is used. This mode implies that the transceiver and the receiver communicate on distinct carriers, and therefore through different propagation channels. Secondly, when considering a receiver on a moving connected vehicle, the transceiver and the receiver communicate one with each other at distinct instants, corresponding to distinct positions of the vehicles, and therefore through different propagation channels. Some works of this thesis propose solutions to obtain space-time focusing for these two scenarios. Finally, some works of this thesis explore the combination of time reversal with other recent signal processing techniques (spatial modulation, on the one hand, a new multi-carrier waveform, on the other hand), or new deployment scenarios (millimeter waves and large antenna arrays to interconnect the nodes of an ultra dense network) or new applications (guidance and navigation) which can be envisaged for future mobile networks.
Janecke, Alex Karl
2011 August 1900
When released into the atmosphere, traditional refrigerants contribute to climate change several orders of magnitude more than a corresponding amount of carbon dioxide. For that reason, an increasing amount of interest has been paid to transcritical vapor compression systems in recent years, which use carbon dioxide as a refrigerant. Vapor compression systems also impact the environment through their consumption of energy. This can be greatly increased by faulty operation. Automated techniques for detecting and diagnosing faults have been widely tested for subcritical systems, but have not been applied to transcritical systems. These methods can involve either dynamic analysis of the vapor compression cycle or a variety of algorithms based on steady state behavior. In this thesis, the viability of dynamic fault detection is tested in relation to that of static fault detection for a transcritical refrigeration system. Step tests are used to determine that transient behavior does not give additional useful information. The same tests are performed on a subcritical air-conditioner showing little value in dynamic fault detection. A static component based method of fault detection which has been applied to subcritical systems is also tested for all pairings of four faults: over/undercharge, evaporator fouling, gas cooler fouling, and compressor valve leakage. This technique allows for low cost measurement and independent detection of individual faults even when multiple faults are present. Results of this method are promising and allow distinction between faulty and fault-free behavior.
<p>3GPP LTE (Long Term Evolution) is a project of the Third Generation Partnership Project to improve the UMTS (Universal Mobile Telecommunications System) mobile phone standard to cope with future technology evolutions. Two duplex schemes FDD and TDD are investigated in this thesis. Several computational intensive components of the baseband processing for LTE uplink such as synchronization, channel estimation, equalization, soft demapping, turbo decoding is analyzed. Cost analysis is hardware independent so that only computational complexity is considered in this thesis. Hardware dependent discussion for LTE baseband SDR platform is given according the analysis results.</p>
Adaptable, scalable, probabilistic fault detection and diagnostic methods for the HVAC secondary systemLi, Zhengwei 30 March 2012 (has links)
As the popularity of building automation system (BAS) increases, there is an increasing need to understand/analyze the HVAC system behavior with the monitoring data. However, the current constraints prevent FDD technology from being widely accepted, which include: 1)Difficult to understand the diagnostic results; 2)FDD methods have strong system dependency and low adaptability; 3)The performance of FDD methods is still not satisfactory; 4)Lack of information. This thesis aims at removing the constraints, with a specific focus on air handling unit (AHU), which is one of the most common HVAC components in commercial buildings. To achieve the target, following work has been done in the thesis. On understanding the diagnostic results, a standard information structure including probability, criticality and risk is proposed. On improving method's adaptability, a low system dependency FDD method: rule augmented CUSUM method is developed and tested, another highly adaptable method: principal component analysis (PCA) method is implemented and tested. On improving the overall FDD performance (detection sensitivity and diagnostic accuracy), a hypothesis that using integrated approach to combine different FDD methods could improve the FDD performance is proposed, both deterministic and probabilistic integration approaches are implemented to verify this hypothesis. On understanding the value of information, the FDD results for a testing system under different information availability scenarios are compared. The results show that rule augmented CUSUM method is able to detect the abrupt faults and most incipient faults, therefore is a reliable method to use. The results also show that overall improvement of FDD method is possible using Bayesian integration approach, given accurate parameters (sensitivity and specificity), but not guaranteed with deterministic integration approach, although which is simpler to use. The study of information availability reveals that most of the faults can be detected in low and medium information availability scenario, moving further to high information availability scenario only slightly improves the diagnostic performance. The key message from this thesis to the community is that: using Bayesian approach to integrate high adaptable FDD methods and delivering the results in a probability context is an optimal solution to remove the current constraints and push FDD technology to a new position.
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