221,850 research outputs found
Control and Filtering for Discrete Linear Repetitive Processes with H infty and ell 2--ell infty Performance
No full textRepetitive processes are characterized by a series of sweeps, termed passes, through a set of dynamics defined over a finite duration known as the pass length. On each pass an output, termed the pass profile, is produced which acts as a forcing function on, and hence contributes to, the dynamics of the next pass profile. This can lead to oscillations which increase in amplitude in the pass to pass direction and cannot be controlled by standard control laws. Here we give new results on the design of physically based control laws for the sub-class of so-called discrete linear repetitive processes which arise in applications areas such as iterative learning control. The main contribution is to show how control law design can be undertaken within the framework of a general robust filtering problem with guaranteed levels of performance. In particular, we develop algorithms for the design of an H? and dynamic output feedback controller and filter which guarantees that the resulting controlled (filtering error) process, respectively, is stable along the pass and has prescribed disturbance attenuation performance as measured by and – norms
"Effect of Temperature on High Shear-Induced Gelation of Charge-Stabilized Colloids without Adding Electrolytes"
No full textWe demonstrated previously (Wu, H.; Zaccone, A.; Tsoutsoura, A.; Lattuada, M.; Morbidelli, M. Langmuir 2009,25, 4715) that, for a colloid stabilized by charges from both polymer chain-end groups and adsorbed sulfonate surfactants, when the surfactant surface density reaches a certain critical value, the shear-induced gelation becomes unachievable at room temperature, even at an extremely large Peclet number, Pe = 4.6 x 10(4). This is due to the presence of the short-range, repulsive hydration force generated by the adsorbed surfactant. In this work, we investigate how such hydration force affects the shear-induced gelation at higher temperatures, in the range between 303 and 338 K. It is found that a colloidal system, which does not gel at room temperature in a microchannel at a fixed Pe = 3.7 x 10(4), does gel when temperature increases to a certain value. The critical initial particle volume fraction for the gelation to occur decreases as temperature increases. These results indicate that the effect of the hydration force oil the gelation decreases as temperature increases. Moreover, we have observed that at the criticality only part of the primary particles is converted to the gel network and the effective particle volume fraction forming the gel network does not change significantly with temperature. The effective particle volume fraction is also independent of the surfactant surface coverage. Since the effective particle volume fraction corresponds to space filling requirement of a standing gel network, which is mainly related to the clusters structure, this result indicates that at a given shear rate the Cluster structure does not change significantly with the surfactant Surface coverage. Oil the other hand, since the cluster morphology is a strong function of the shear rate, we have observed that when the Peclet number is lowered from Pe = 3.7 x 10(4) to 1.7 x 10(4), the effective particle Volume fraction reduces from 0.19 to 0.12 at 3 13 K
Wu, Chieh-ping -- 1981-82 -- Correspondence, Individual -- letter, 1981-02-20
No full textLetter from Knisely, William H. to Wu, Chieh-Ping dated 1981-02-20.Sabin Collection Fair Use Policy</a
Reticularisus Wu, Wu & Han, a new subgenus of the genus Rhamnosa Fixsen, 1887 from China, with description of a new species (Lepidoptera: Limacodidae)
No full textA new subgenus, ReticularisusWu, Wu & Han, subgen. n., with type species Rhamnosa henanensis Wu, 2008,of the genus Rhamnosa Fixsen, 1887 is described and illustrated. For the sake of contrast, the type species of theother two subgenera in this genus have been given, including adults and male genitalia. Rhamnosa (Reticularisus) shierbeihoua Wu, Wu & Han, sp. n., a Limacodidae collected from the southwest of China is described as new to science. Also, the new species is illustrated with images of the adult and male genitalia and compared with the similar species Rh. henanensis.Se describe e ilustra un nuevo subgénero, Reticularisus Wu, Wu & Han, subgen. n., con la especie tipo Rhamnosa henanensis Wu, 2008, del género Rhamnosa Fixsen, 1887. Para contrastar, se da la especie tipo de los otros dos subgéneros en este género, incluyendo los adultos y la genitalia del macho. Se describe como nueva para la ciencia a Rhamnosa (Reticularisus) shierbeihoua Wu, Wu & Han, sp. n., un Limacodidae capturado del suroeste de China. También la nueva especie es ilustrada con imágenes del adulto y genitalia del macho y comparada con la especie similar Rh. henanensis
Patchy Colloidal Particles Via Surfactant Adsorption: Interactions and Gels of Tunable Structure
No full textThe presence of charged molecules attached on the surface of Brownian particles can dramatically affect their mutual interaction as well as their interactions with foreign surfaces. With respect to aggregation, the coexistence of domains of charged adsorbed molecules and hydrophobic domains on polymer colloids opens up the possibility of tuning the interactions in a wide range from homogeneously hydrophobic surfaces to completely hydrophilic repulsive surfaces with strong hydration forces. In a well characterized system made of styrene-acrylate copolymer particles and two different ionic surfactants, aliphatic C-18 carboxylate and aliphatic C-15 sulfonate, we have shown experimentally by means of laser light scattering that an initial, gas-like state of noninteracting adsorbed molecules laying down to the particle surface is followed, with increasing surfactant concentration, by the formation of condensed domains prior to reaching full coverage of the particle surface. In the low salt limit, by shearing the dispersion at very high shear-rate in a microchannel, it is shown that the surfactant domains on two particles can fuse/adhere leading to aggregation as long as an even small-sized uncovered polymer patch is present and aggregation is always possible on the free hydrophobic polymer patches. In the case of fully developed films, by analyzing the mechanism of shear aggregation in the low-salt limit theoretically, we show that short-range hydration repulsive forces dominate over DLVO forces and adhesion/aggregation can never be achieved even upon application of extremely high collision energies. We can also provide evidence that gels obtained by shearing the dispersion at high-shear rate at low-salt exhibit a structure that is strongly affected by the degree of coverage of surfactant, i.e. by the relative extension of charged-hydrophilic to hydrophobic patches. The fractal dimension of the gel can indeed vary from 2.1 at high surfactant coverage where only a few small patches are available for aggregation (valence-limited case) to 2.8 at low surfactant coverage where the gel is made of very compact clusters. This finding unfolds new possibilities for making engineered mesoscopic disordered materials by tuning the surface properties at microscopic level.
Zaccone, Wu, Lattuada and Morbidelli, Journal of Physical Chemistry B, 112, 1976 (2008)
Zaccone, Wu, Lattuada and Morbidelli, Journal of Physical Chemistry B, in pres
Mrs. T. H. Wu, Mildred Wu, and Barbara Wu with fireworks for Chinese New Year celebration, 1937
No full textPhotograph shows Mrs. T. H. Wu and the girls in a room with a display of the Chinese fireworks.;From the San Antonio Light negative box no. 1540
Mrs. T. H. Wu, Mildred Wu, and Barbara Wu with fireworks for Chinese New Year celebration, 1937
No full textPhotograph shows Mrs. T. H. Wu and the girls in a room with a display of the Chinese fireworks.;From the San Antonio Light negative box no. 1540.
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