Effect of coal-over-coal reburn on furnace temperature and heat flux distributions in 1 MW tangentially fired furnace

The furnace temperature and heat flux distributions of 1 MW tangentially fired furnace were studied during coal-over-coal reburn, and the influences of the position of reburn nozzle and reburn fuel fraction on furnace temperature and heat flux distributions were investigated. Compared with the baseline, the flue gas temperature is 70–90 C lower in primary combustion and 130–150 C higher at furnace exit, and the variations of the flue gas temperature distributions along furnace height are slower. The temperature distribution along the width of furnace wall decreases with the increase of the relative furnace height. In the primary combustion zone and the reburn zone, the temperature and heat flux distributions of furnace wall are much non-uniform and asymmetric along the width of furnace wall, those of furnace wall in the burnout zone are relatively uniform, and the temperature non-uniformity coefficients of the primary combustion zone, the reburn zone and the burnout zone are 0.290, 0.100 and 0.031, respectively.

Estimation and inference for grasping and manipulation tasks using vision and kinesthetic sensors

This thesis presents a novel framework for state estimation in the context of robotic grasping and manipulation. The overall estimation approach is based on fusing various visual cues for manipulator tracking, namely appearance and feature-based, shape-based, and silhouette-based visual cues. Similarly, a framework is developed to fuse the above visual cues, but also kinesthetic cues such as force-torque and tactile measurements, for in-hand object pose estimation. The cues are extracted from multiple sensor modalities and are fused in a variety of Kalman filters.

A hybrid estimator is developed to estimate both a continuous state (robot and object states) and discrete states, called contact modes, which specify how each finger contacts a particular object surface. A static multiple model estimator is used to compute and maintain this mode probability. The thesis also develops an estimation framework for estimating model parameters associated with object grasping. Dual and joint state-parameter estimation is explored for parameter estimation of a grasped object's mass and center of mass. Experimental results demonstrate simultaneous object localization and center of mass estimation.

Dual-arm estimation is developed for two arm robotic manipulation tasks. Two types of filters are explored; the first is an augmented filter that contains both arms in the state vector while the second runs two filters in parallel, one for each arm. These two frameworks and their performance is compared in a dual-arm task of removing a wheel from a hub.

This thesis also presents a new method for action selection involving touch. This next best touch method selects an available action for interacting with an object that will gain the most information. The algorithm employs information theory to compute an information gain metric that is based on a probabilistic belief suitable for the task. An estimation framework is used to maintain this belief over time. Kinesthetic measurements such as contact and tactile measurements are used to update the state belief after every interactive action. Simulation and experimental results are demonstrated using next best touch for object localization, specifically a door handle on a door. The next best touch theory is extended for model parameter determination. Since many objects within a particular object category share the same rough shape, principle component analysis may be used to parametrize the object mesh models. These parameters can be estimated using the action selection technique that selects the touching action which best both localizes and estimates these parameters. Simulation results are then presented involving localizing and determining a parameter of a screwdriver.

Lastly, the next best touch theory is further extended to model classes. Instead of estimating parameters, object class determination is incorporated into the information gain metric calculation. The best touching action is selected in order to best discern between the possible model classes. Simulation results are presented to validate the theory.

The cast net fishery, Kainji Lake, Nigeria 1970-1997

This study was carried out to establish trends in the cast net fishery of Kainji Lake, Nigeria. The cast net fishery was second in importance to the gillnet fishery in the early years after impoundment of the lake and still continues to be an important component of the fishery. Some of the economically important species such as Citharinus spp, Tilapia spp, Labeo spp, Alestes spp and Synodontis spp are exploited by cast nets. The study has not revealed any drastic perturbation in the species diversity, catch composition, and any real ecosystem overfishing. On the other hand, both the catfish, Auchenoglanis spp and the predator Hydrocynus spp appear to have increased in the catch in recent years. Never-the-less there is a decline in the mean weight of the major exploited fish species due to the capture of under sized fishes without allowing them to grow to 'legally' marketable sizes. The use of small meshed cast net and also fishing in the shallow waters of the lake can give rise to this situation. Thus, there are signs of growth overfishing in the fish stocks. It must also be acknowledged that the situation is complicated by the fact that in a multi-gear fishery as on Kainji Lake, the cast net fishery could not be managed in isolation without due regard to the other competing gears. The catch per unit of effort (CPUE) has declined in the cast net fishery possibly due to the increase in effort by the major fishing gears over the years. The ongoing extension campaigns by the KLFPP appears to be having the desired effect, as there was reduction in the number of the major fishing gears on the Lake in 1997. It can be anticipated that if this trend continues, the CPUE will recover in the long run. Yields observed from the mesh selectivity study revealed that for major species in the cast net fishery, both by number and weight, were maximal at 2.5 inch mesh, which contrasts with the fact that current minimum allowable mesh in the Fisheries Edict for the Lake is 2.0 inch. The adoption of 2.5 inch as the minimum allowable mesh in the cast net fishery is recommended to be included in future revision of existing regulations. It is also recommended that for this control to have a desired effect, the casting of the net from the shore should be prohibited so as to reduce the incidence of juvenile mortality in the nursery areas. (PDF contains 28 pages)

Jungfischsituation in der Nordsee wenig ermutigend

In order to investigate the abundanceand strength of most recent year classes of cod,haddock, whiting, Norway pout, herring, sprat, and mackerel seven researchvessels of ICES member states carried out a bottom trawl survey in the North Sea in January/February 1996. Germany took part in these investigations by R.V. "Walther Herwig III" from January 19 to February 9 covering 62 out of 332 international stations. No substantial positive or negative results concerning the incoming year classes were obtained. As expected, the hydrographc situation of the area under investigation was strongly influenced by the actual weather: On the one hand, the continuous cooling of the surface layer by cold air caused vertical mixing down into the bottom layer in larger areas, and led to decreasing water temperatures which were below the long term values in nearly all the North Sea at the end of the investigation period. On the other hand, the continuous southern to eastern winds over the North Sea led to horizontal water mass transports renewing vertical salinity differences and inducing regionally positive as weH as negative salinity anomalies of up to 0.6· 10-3. ,

The long road of climate negotiations: From Kyoto to Paris stopping over in Doha

4 p.

Breaking the 400 ppm barrier: Physical and Social implications of the recent CO2 rise

6 p.

Rompiendo la barrera de las 400 ppm: implicaciones físicas y sociales del reciente aumento de CO2

6 p.

400 ppm-ko langa hautsi da: CO2-kontzentrazioaren igoeraren ondorio fisiko eta sozialak

6 p.

Ancillary ligand effects : from zirconium(IV)-catalyzed homogeneous propylene polymerization to platinum(II)-mediated C-H bond activation

A series of C_s- and C₁-symmetric doubly-linked ansa-metallocenes of the general formula {1,1'-SiMe₂-2,2'-E-('ƞ⁵-C₅H₂-4-R¹)-(ƞ⁵-C₅H-3',5'-(CHMe₂)₂)}ZrC₂ (E = SiMe₂ (1), SiPh₂ (2), SiMe₂ -SiMe₂ (3); R¹ = H, CHMe₂, C₅H₉, C₆H₁₁, C₆H₅) has been prepared. When activated by methylaluminoxane, these are active propylene polymerization catalysts. 1 and 2 produce syndiotactic polypropylenes, and 3 produces isotactic polypropylenes. Site epimerization is the major pathway for stereoerror formation for 1 and 2. In addition, the polymer chain has slightly stronger steric interaction with the diphenylsilylene linker than with the dimethylsilylene linker. This results in more frequent site epimerization and reduced syndiospecificity for 2 compared to 1.

C₁-Symmetric ansa-zirconocenes [1,1 '-SiMe₂-(C₅H₄)-(3-R-C₅H₃)]ZrCl₂ (4), [1,1 '-SiMe₂-(C₅H₄)-(2,4-R₂-C₅H₂)]ZrCl₂ (5) and [1,1 '-SiMe₂-2,2 '-(SiMe₂-SiMe₂)-(C₅H₃)-( 4-R-C₅H₂)]ZrCl₂ (6) have been prepared to probe the origin of isospecificity in 3. While 4 and 3 produce polymers with similar isospecificity, 5 and 6 give mostly hemi-isotactic-like polymers. It is proposed that the facile site epimerization via an associative pathway allows rapid equilibration of the polymer chain between the isospecific and aspecific insertion sites. This results in more frequent insertion from the isospecific site, which has a lower kinetic barrier for chain propagation. On the other hand, site epimerization for 5 and 6 is slow. This leads to mostly alternating insertion from the isospecific and aspecific sites, and consequently, a hemi-isotactic-like polymers. In comparison, site epimerization is even slower for 3, but enchainment from the aspecific site has an extremely high kinetic barrier for monomer coordination. Therefore, enchainment occurs preferentially from the isospecific site to produce isotactic polymers.

A series of cationic complexes [(ArN=CR-CR=NAr)PtMe(L)]⁺[BF₄]⁺ (Ar = aryl; R = H, CH₃; L = water, trifluoroethanol) has been prepared. They react smoothly with benzene at approximately room temperature in trifluoroethanol solvent to yield methane and the corresponding phenyl Pt(II) cations, via Pt(IV)-methyl-phenyl-hydride intermediates. The reaction products of methyl-substituted benzenes suggest an inherent reactivity preference for aromatic over benzylic C-H bond activation, which can however be overridden by steric effects. For the reaction of benzene with cationic Pt(II) complexes, in which the diimine ligands bear 3,5-disubstituted aryl groups at the nitrogen atoms, the rate-determining step is C-H bond activation. For the more sterically crowded analogs with 2,6-dimethyl-substituted aryl groups, benzene coordination becomes rate-determining. The more electron-rich the ligand, as reflected by the CO stretching frequency in the IR spectrum of the corresponding cationic carbonyl complex, the faster the rate of C-H bond activation. This finding, however, does not reflect the actual C-H bond activation process, but rather reflects only the relative ease of solvent molecules displacing water molecules to initiate the reaction. That is, the change in rates is mostly due to a ground state effect. Several lines of evidence suggest that associative substitution pathways operate to get the hydrocarbon substrate into, and out of, the coordination sphere; i.e., that benzene substitution proceeds by a solvent- (TFE-) assisted associative pathway.

La cerámica de la Segunda Edad del Hierro en el País Vasco: Estudio tecnológico, funcional y social

670 p. Capítulos de introducción, metodología, discusión y conclusiones en castellano e inglés.