Blends of polyamide-6 with acrylic core-shell impact modifiers

Blends of polyamide-6 (PA6) and acrylic core-shell impact modifiers (CSIM) were made by an extruder process as well as a reactor process. On the extruder blends, the impact behaviour was studied as a function of temperature while changing the type of CSIM, the CSIM concentration (0¿40%) and the blending conditions. Reactor blends were prepared from caprolactam/CSIM mixtures via a hydrolytic polymerization process initiated either with water or with aminocapronic acid. The aminocapronic acid-initiated process is faster. The influence of reaction conditions on the deagglomeration of the CSIM, the melt flow index and the impact behaviour of the blends were studied. The degree of grafting of PA6 on the CSIM and the melt rheological behaviour of some samples have been investigated. The CSIM agglomerates were found to be broken up in the caprolactam starting mixture and did not coalesce to bigger particles. With the reactor blend method, often highly viscous melts were obtained. This is probably due to the formation of a comb-like structure of CSIM chains dissolved in caprolactam to which PA6 chains had been grafted

Subword-based Indexing for a Minimal False Positive Rate

Subword-based Indexing for a Minimal False Positive Rat

Graduate-level Instructor’s Perception of Teaching Critical Thinking

Higher learning institutions identify the teaching of critical thinking skills to students as a goal of the academic programs offered. This study examined faculty perceptions for teaching critical thinking skills

Evaluation of noisy transcripts for spoken document retrieval

Spoken Document Retrieval (SDR) is usually implemented by using an Information Retrieval (IR) engine on speech transcripts that are produced by an Automatic Speech Recognition (ASR) system. These transcripts generally contain a substantial amount of transcription errors (noise) and are mostly unstructured. This thesis addresses two challenges that arise when doing IR on this type of source material: i. segmentation of speech transcripts into suitable retrieval units, and ii. evaluation of the impact of transcript noise on the results of an IR task.\ud It is shown that intrinsic evaluation results in different conclusions with regard to the quality of automatic story boundaries than when (extrinsic) Mean Average Precision (MAP) is used. This indicates that for automatic story segmentation for search applications, the traditionally used (intrinsic) segmentation cost may not be a good performance target. The best performance in an SDR context was achieved using lexical cohesion-based approaches, rather than the statistical approaches that were most popular in story segmentation benchmarks.\ud For the evaluation of speech transcript noise in an SDR context a novel framework is introduced, in which evaluation is done in an extrinsic, and query-dependent manner but without depending on relevance judgments. This is achieved by making a direct comparison between the ranked results lists of IR tasks on a reference and an ASR-derived transcription. The resulting measures are highly correlated with MAP, making it possible to do extrinsic evaluation of ASR transcripts for ad-hoc collections, while using a similar amount of reference material as the popular intrinsic metric Word Error Rate.\ud The proposed evaluation methods are expected to be helpful for the task of optimizing the configuration of ASR systems for the transcription of (large) speech collections for use in Spoken Document Retrieval, rather than the more traditional dictation tasks

Mapping shoreline indicators on a sandy beach with supervised edge detection of soil moisture differences

This study describes a method to map shoreline indicators on a sandy beach. The hypothesis is that, on this beach, spectral albedo is predominantly determined by moisture content and water lines can, therefore, be detected as albedo contrasts. A laboratory experiment is performed to relate moisture content to image albedo, and supervised edge detection is subsequently used to map the shoreline indicators with remote sensing imagery. The algorithm is tested with data from visible, near-infrared and shortwave-infrared wavelength regions. These results are compared to shoreline indicators obtained by a field survey and a shoreline indicator derived from a digital elevation model. Both the water line present when the imagery was acquired, as well as the maximum extent of the last flood, can be detected as a single edge. Older high water lines are confused with the last high water line and appear dispersed, as there are multiple debris lines present on the beach. The low water line, usually in saturated sand, also appears dispersed due to the presence of channels and troughs. Shorelines are constant moving boundaries, which is why shoreline indicators are used as a proxy. Unlike a mathematical indicator that is based on an elevation model, our method is more sensitive to the dynamic nature of shorelines. Supervised edge-detection is a technique for generating reproducible measurements of shoreline indicator positions over time, and aids in the monitoring of coastline migration

The assessment of hypospadias

Hypospadias is a congenital anomaly involving the anterior urethra that can atTect both men and women. The dcfonnity is characterised by a dystopia of the extemal ori1ice of the urethra and can be associated with a curvahu'c of the penile body in male subjects. The incidence of hypospadias in men is estimated as one in two to three hundred live male bilths and seems to be increasing although it varies according to the registration system used, geographical area and racial influences I. The precise aetiology of this anomaly remains unclear, although certain risk factors can be assessed. For instance, hypospadias is known to cluster in families but little else is definitive about the genetics involved in its aetiology and it still seems to be a multifactorial anomaly 2-6. Early exposure to progestins in utero during organogenesis also appears to be of influence in the development of hypospadias with a twofold relative risk 7. Because of the sporadicness of this exposure and hypospadias it is, however, difficult to demonstrate a definitive association J. Another factor held responsible as a possible cause of hypospadias is a local vascular insufiiciency of the embryo during pregnancy~. The morphogenesis of the male external genital system and therefore the hypospadias def01l11ity as well, have been the subject of controversy in the past 9-11. Glenister, a lecturer at the Charing Cross Hospital Medical School in London, contributed a substantial amount of knowledge on thc development of the male external genital 9.12.13. His general concept of the cmbryogenesis of the male anterior urethra has had velY little opponents in the literature. Some details, such as the fonnation of the glandular part of the urethra or the onset of preputial dcvelopment, are challenged by others 14-18. Searching for cellbiological mechanisms like cell proliferation and apoptosis, responsible for normal development of the male genital system, it is striking to find nothing on this subject in the literahlre