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An experimental method was developed for quantifying mineral scale nucleation and growth on RO membranes enabling comparison of the effectiveness of antiscalants in retarding mineral scale formation. Mineral scale growth and inhibition was evaluated, for calcium sulfate dihydrate (gypsum) as a model scalant, from direct visual observations of crystal growth on the membrane surface in a plate-and-frame RO cell. Comparison of membrane scaling with and without the use of antiscalants was carried out based on RO scaling tests conducted under identical operating conditions with respect to the initial flux and crossflow velocity, at identical initial concentration fields within the RO membrane channel and at the membrane surface. The range of gypsum saturation index (SIg) at the membrane surface was 1.3–2.3 enabling determination of gypsum scaling for the above SIg range from a single RO scaling test, given direct observation of crystal nucleation and growth on the membrane surface. The present work demonstrates that it is possible to distinguish antiscalants modes of scale inhibition and corresponding scale suppression effectiveness, over a reasonable range of solution supersaturation. The current approach introduces antiscalant crystal nucleation and growth retardation factors that can aid in the development, selection and dose optimization of antiscalants for use in RO desalination.

A 3-D (3-dimensional) numerical modeling approach to analyze the coupling of mineral scale, concentration polarization and permeate flux was developed and demonstrated for a gypsum membrane scaling test in a plate-and-frame RO membrane module geometry. The impact of concentration polarization on mineral gypsum scaling, and in turn the impact of mineral scale on the concentration polarization field, were explored via 3-D finite-element numerical solutions of the coupled fluid hydrodynamics and solute mass transfer equations, along with detailed experimental data on the extent and location of mineral scale. Numerical simulations of the concentration field for a scale-free membrane revealed that the regions of highest supersaturation with respect to calcium sulfate corresponded to regions of highest gypsum scale density, as observed through real-time imaging of the membrane surface in the gypsum scaling test. 3-D simulations of the concentration field in the presence of mineral scale revealed that the concentration polarization modulus and permeate flux were largely unaffected in contiguous scale-free regions of the membrane. However, near and just downstream of individual crystal formations, the local concentration polarization modulus decreased (by ∼5%) and the permeate flux increased (by ∼2%) relative to the same positions in the absence of scale. The model-calculated and experimental permeate flux decline agreed closely with an average absolute error of 1.8%. The present study suggests that flux decline due to mineral scaling can be reasonably described by the surface blockage mechanism.

Motivated by colour constancy work in physics-based vision, we develop a new low-dimensional video frame feature that is effectively insensitive to lighting change and apply the feature to keyframe production using hierarchical clustering. The new image feature results from normalising colour channels for frames and then treating 2D histograms of chromaticity as images and compressing these. Because we effectively reduce any video to the same lighting conditions, we can precompute a universal basis on which to project video frame feature vectors. The new feature thus has the advantage of more expressively capturing essential colour information, and is useful for video indexing because it is very low-dimension—the feature vector is only of length 8. We carry out clustering efficiently by adapting the hierarchical clustering data structure to temporally-ordered clusters. Using a new multi-stage hierarchical clustering method, we merge clusters based on the ratio of cluster variance to variance of the parent node, merging only adjacent clusters, and then follow with a second round of clustering. The second stage merges clusters incorrectly split in the first round by the greedy hierarchical algorithm, and as well merges non-adjacent clusters to fuse near-repeat shots. The new summarization method produces a very succinct set of keyframes for videos and, compared to a previous well-known technique, results are excellent.

When asked to read a text, people who stutter produce dysfluencies that can be divided into two types. These are (a) those dysfluencies that mainly influence production of individual lexical items and (b) those involving, either alone or in combination, omitting words, inserting incorrect words and repeating phrases. In case (a), the speech breakdowns are termed lexical dysfluencies (LD). LD include word and part-word repetitions, prolongations, and broken words. The dysfluencies in (b) are termed supralexical (SD). This class comprises interjections, revisions, incomplete phrases, and phrase repetitions. If SD and LD are not distinguished, then the way certain dysfluent words should be categorized is inherently ambiguous. For instance, there is no a priori way of deciding how to categorize an LD that occurs within a group of words comprising an SD. The proposed solution to this problem involves locating and processing SD before LD. Doing this allows any LD that occurs within a group of words that can also be designated as an SD to be assessed and removed from further consideration prior to location of isolated LD (the LD that occur within an SD are, then, subordinate to the SD). A computer-based parser that locates SD in transcriptions of read text is described. Its performance is compared with that of human judges.

Conflicting findings have been reported concerning whether fluent children use more complex syntactic structures than stutterers and whether or not stutterers experience specific difficulty with complex syntactic structures. On critical examination, the first of these apparent discrepancies appears to be due to (a) differences in the methods employed for syntactic analysis in different studies, and (b) misleading impressions gained by looking at speakers within a single age range. Data were reanalyzed where one method of analysis had shown that fluent speakers and stutterers did not differ with regard to syntactic structures used but where they did show a propensity for stuttering to occur on complex syntactic structures. These data cover a range of age groups. When the second method of syntactic analysis was applied, a difference was found between fluent speakers and stutterers, with the stutterers initially using more simple structures and fewer complex ones. This difference decreased over age groups. However, a difference still remained with respect to which syntactic structures stutterers experience difficulty. An additional analysis, not formerly conducted on these data, showed that, as reported elsewhere, there was a higher probability of stuttering on clause-initial and. It was also shown that this tendency decreased with age group of the stutterers.

Though the phonological difficulty of a word might reasonably be supposed to influence whether a word is stuttered, it has recently been reported that the incidence of stuttering does not depend on this factor in child stutterers. This conclusion is reexamined in the current report. Data are employed that were obtained from groups of child stutterers (and their controls) who vary in age and severity of their disorder. First, it is shown that the measure of phonological difficulty reveals differences in phonological ability for children of different ages (stutterers and fluent controls). The properties of words with regard to whether they are function words or content words, their position in the sentence, their length, and the phoneme that they start with vary between phonological categories (referred to as “Brown's factors”). Since these factors could influence whether words are stuttered in their own right, they may led to apparent differences in stuttering between words in different phonological categories that are spurious. Alternatively, these factors may disguise influences that phonological categories have on stuttering. It is shown in the next analysis that the words in the various phonological categories differ with regard to Brown's factors. In the final analysis, the proportion of words stuttered for words in each phonological category are analyzed so that any influence Brown's factors might have are removed by treating the factors as covariates. No dependence of stuttering on phonological category is observed for age group, stutterer's severity, or word types (stuttered word or word following the stuttered word). Thus, phonological difficulty as measured here and elsewhere does not appear to be a major factor governing the incidence of stuttering in children.