Machine learning approaches to improving mispronunciation detection on an imbalanced corpus

This thesis reports the investigations into the task of phone-level pronunciation error detection, the performance of which is heavily affected by the imbalanced distribution of the classes in a manually annotated data set of non-native English (Read Aloud responses from the TOEFL Junior Pilot assessment). In order to address problems caused by this extreme class imbalance, two machine learning approaches, cost-sensitive learning and over-sampling, are explored to improve the classification performance. Specifically, approaches which assigned weights inversely proportional to class frequencies and synthetic minority over-sampling technique (SMOTE) were applied to a range of classifiers using feature sets that included information about the acoustic signal, the linguistic properties of the utterance, and word identity. Empirical experiments demonstrate that both balancing approaches lead to a substantial performance improvement (in terms of f1 score) over the baseline on this extremely imbalanced data set. In addition, this thesis also discusses which features are the most important and which classifiers are most effective for the task of identifying phone-level pronunciation errors in non-native speech

A Novel Method of Multispectral Imagery Registration Based on Minor and Noise Component Criterion

AbstractFor multispectral imagery, spatial registration between bands is a very important part of the overall quality of the multispectral imagery product. In this paper, a multispectral imagery registration method is presented. It takes minor and noise component of sample covariance matrix as measure criterion, utilizes mutual information method to create registration seed sources, uses smooth filter to extend trapping width of registration curve. Experiments were conducted using multispectral imagery from the ETM Satellite. Control points optimal searching experiments show that the presented method can improve the efficiency and accuracy of multispectral imagery registration greatly

Dry Powder Microfeeding System for Solid Freeform Fabrication

Second generation SFF techniques allow both composition and shape to be downloaded directly from a computer file so that 3D functionally graded materials (FGM) can be assembled. Methods for multi-material deposition are also needed in combinatorial research, colour management and pharmaceutical dosing. In this work, computer-controlled microfeeding systems using ultrasonic vibration of a capillary were built. A wide range of stable flow rate control and switching control were achieved in the acoustic vibration system, and uniform powder doses were obtained in the ultrasonic system. The experimental results show that the nozzle diameter, transmission fluid depth, waveforms, voltage amplitude, frequency and oscillation duration all influence the dose mass. Among these factors, the nozzle diameter, voltage amplitude and oscillation duration can be used to control the dose mass. Raster printing of patterns with various resolution and dot size are demonstrated.Mechanical Engineerin

Ureteric Obstruction Caused by a Migrated Intrauterine Device

AbstractWe present an extremely rare case of ureteric obstruction caused by a migrated intrauterine device. A 36-year-old female with complaints of almost 10 months left flank pain presented to our hospital. She used an IUD for contraception for 6 months after the birth of her first child. The IUD was not visible then. Ultrasonography (US) revealed that left severe hydronephrosis and upper ureterectasis. Pelvic computed tomography (CT) found that IUD was located very close to the lower ureter which was adjacent to the third anatomize physiological narrow. Laparoscopy was performed to remove the migrated IUD. After 5 months of surgery, left hydronephrosis was exacerbated. This time we chose to perform the ureterocystostomy to relieve the hydronephrosis. We reported this rare case to remind that we must keep alert to the loss of the IUD to prevent it may cause severe injury of the nearby organs. IUD must be carefully researched for possible perforation of the uterus and migration to the pelvic organs