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31.
Biological wastewater treatment generates huge amounts of waste sludge which need to be dewatered and eventually dried to minimize transportation and incineration costs. A characteristic feature of sludge in this context is that it turns into a sticky substance during its drying process inducing fouling problems in the drying installation. At the wastewater treatment plant of Monsanto in Antwerp, Belgium, one enclosed centrifuge-dryer system is used to dry the sludge. In the past, this installation had to be shut down regularly due to dryer fouling problems. To avoid these operational problems, a binary logistic regression analysis is presented in this research based on a 5-year database, resulting in an empirical model for the evaluation of the dryer fouling risk as a function of the sludge feed characteristics. The model inputs are the sludge volume index (SVI) and the dosing of clay additive and tertiary (flotation) sludge, the latter containing polyaluminumchloride (PACl), to the sludge feed of this particular system.By exploiting the knowledge captured by this model, the derived control strategy is based on the value of the SVI. Whenever the SVI is high the original high clay dosing to the feed needs to be maintained. At moderate SVI values, implying an intrinsically better sludge dewaterability, the strategy dictates a reduction in the clay dosing to the sludge feed to have a reduced sludge solids dryness after dewatering, thereby avoiding that the sludge exhibits its most sticky phase when passing the most fouling sensitive part of the dryer. When the SVI is lower than 50 mL/g the control strategy states that conditioning of the sludge with PACl is required to mask the stickiness instead of postponing it, avoiding that the stickiness of the sludge already hampers the dewatering stage of the process.  相似文献   
32.
Various machine learning problems rely on kernel-based methods. The power of these methods resides in the ability to solve highly nonlinear problems by reformulating them in a linear context. The dominant eigenspace of a (normalized) kernel matrix is often required. Unfortunately, the computational requirements of the existing kernel methods are such that the applicability is restricted to relatively small data sets. This letter therefore focuses on a kernel-based method for large data sets. More specifically, a numerically stable tracking algorithm for the dominant eigenspace of a normalized kernel matrix is proposed, which proceeds by an updating (the addition of a new data point) followed by a downdating (the exclusion of an old data point) of the kernel matrix. Testing the algorithm on some representative case studies reveals that a very good approximation of the dominant eigenspace is obtained, while only a minimal amount of operations and memory space per iteration step is required.  相似文献   
33.
This paper studies the stability of a class of PID controller to stabilize robot manipulators with elastic joints. It is shown that a PD action on the rotor position and an integral control action on the link position suffice to provide semiglobal asymptotic stability of the desired link position.  相似文献   
34.
This study examined problematic gaming behavior and depressive tendencies among people who play different types of online-games. Other game-related variables were investigated to determine if other differences between three game types could be established. Participants in the current research (n = 468) can be classified into three independent groups. Subjected users either solely played massive multiplayer online role-playing games (MMORPGs) or they preferred online-ego-shooters (OES) or real-time-strategy games (RTS). Results indicate that MMORPG users show more often problematic gaming behavior, depressive tendencies and lower self-esteem compared to users playing other online-games. MMORPG users reported to playing significantly more often in order to escape from real-life problems, which might be a valuable coping strategy but might also lead to problematic gaming behavior.  相似文献   
35.
Efficient resource management is mandatory to achieve maximum system capacity for next generation communications systems. Resource management deals with the available spectral band, time, power, and space for a transmission signal. It includes (i) the frequency planning, (ii) the selection of transmit power, and (iii) the assignment of the channels and access nodes to the users. The paper presents a generalized notation as well as graph algorithms for resource management problems. Impairment graphs can be used for frequency planning, whereas flow graphs are suitable for channel access problems. To evaluate the performance of the resource management, service criteria (such as blocking or the carrier to interference ratio C/I) or efficiency criteria (bandwidth requirements) can be derived from the graphs. The resource management techniques are applied to satellite networks with non‐geostationary orbits yielding time‐variant network topologies. As a simple example, the channel assignment and capacity optimization of the EuroSky Way system are shown. Furthermore, a comparison of fixed, dynamic and hybrid channel allocation schemes (FCA, DCA, HCA) for a typical MEO satellite scenario is given. Satellite diversity and its impact on bandwidth requirement and transmission quality is also examined. Finally, it is shown how spread spectrum systems can be investigated with the presented tools. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   
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