A study of arithmetically symmetrical bandpass filters

Call number: LD2668 .R4 1966 Y9

Efficient audio signal processing for embedded systems

We investigated two design strategies that would allow us to efficiently process audio signals on embedded systems such as mobile phones and portable electronics. In the first strategy, we exploit properties of the human auditory system to process audio signals. We designed a sound enhancement algorithm to make piezoelectric loudspeakers sound "richer" and "fuller," using a combination of bass extension and dynamic range compression. We also developed an audio energy reduction algorithm for loudspeaker power management by suppressing signal energy below the masking threshold. In the second strategy, we use low-power analog circuits to process the signal before digitizing it. We designed an analog front-end for sound detection and implemented it on a field programmable analog array (FPAA). The sound classifier front-end can be used in a wide range of applications because programmable floating-gate transistors are employed to store classifier weights. Moreover, we incorporated a feature selection algorithm to simplify the analog front-end. A machine learning algorithm AdaBoost is used to select the most relevant features for a particular sound detection application. We also designed the circuits to implement the AdaBoost-based analog classifier.PhDCommittee Chair: Anderson, David; Committee Member: Hasler, Jennifer; Committee Member: Hunt, William; Committee Member: Lanterman, Aaron; Committee Member: Minch, Bradle

Measurement of elemental speciation by liquid chromatography: inductively coupled plasma mass spectrometry (LC-ICP-MS) with the direct injection nebulizer (DIN)

A new version of the direct injection nebulizer (DIN) is used to interface liquid chromatographic (LC) separations with element - selective detection by inductively coupled plasma - mass spectrometry (ICP-MS). The advantages of using LC-DIN-ICP-MS include little dead volume, low sample and solvent consumption, excellent plasma stability when nebulizing samples containing concentrated organic solvent, excellent absolute detection limits, excellent precision, superior chromatographic resolution, and reduced memory effects from memory-prone elements (e.g., Hg);Various compounds containing arsenic (AsO[subscript]2[superscript]-, HAsO[subscript]4[superscript]2-, CH[subscript]3AsO[subscript]3[superscript]2- and (CH[subscript]3)[subscript]2AsO[subscript]2[superscript]-), tin (CH[subscript]3Sn[superscript]3+, (CH[subscript]3)[subscript]2Sn[superscript]2+, (C[subscript]2H[subscript]5)[subscript]2Sn[superscript]2+ and (CH[subscript]3)[subscript]3Sn[superscript]+), mercury (Hg[superscript]+2, CH[subscript]3Hg[superscript]+, C[subscript]2H[subscript]5Hg[superscript]+ and C[subscript]6H[subscript]5Hg[superscript]+) and lead (Pb[superscript]+2, (CH[subscript]3)[subscript]3Pb[superscript]+ and (C[subscript]2H[subscript]5)[subscript]3Pb[superscript]+) are separated by reversed-phase ion-pairing LC. Selenium species (SeO[subscript]3[superscript]2- and SeO[subscript]4[superscript]2-) are separated by ion chromatography (IC). Several metalloproteins containing Na, Fe, Cu, Zn, Cd, Ba, and Pb are separated by size-exclusion chromatography (SEC). Some of these compounds are separated and measured in biological and environmental samples such as human urine and human serum. Detection limits are ≈3, 0.7, 1, 0.5, 5, 0.5, 15, 7, and 0.2 pg for Fe, Cu, Zn, As, Se, Cd, Sn, Hg, and Pb, respectively. Microbore (1-2 mm i.d.) packed columns are employed because the liquid flow rates used (30-100 [mu]L min[superscript]-1) are compatible with the DIN;Aerosol droplet sizes and velocities from a DIN are measured with radial and axial spatial resolution by phase doppler particle analysis (PDPA). The droplets on the central axis of the spray become finer and their size becomes more uniform when ≈20% methanol is added to the usual aqueous solvent. This could explain why the analyte signal is a maximum at this solvent composition when the DIN is used for ICP-MS. Mean droplet velocities are 12 to 22 m s[superscript]-1 with standard deviations of ±4 to ±7 m s[superscript]-1. The outer fringes of the aerosol plume tend to be enriched in large droplets. The Sauter mean diameter (D[subscript]3,2) and velocity of the droplets also vary substantially with axial position in the aerosol plume. These findings are valuable for improving the analytical performance of the DIN

A Review on the Alzheimer Disease Animal Models and Retinal Degeneration

Alzheimer’s disease (AD) is a chronic neurodegen- erative disease, serving as the most common form of dementia among the elderly population. AD targets various neurological processes in humans such as the visual pathway and hence resulting in various forms of visual abnormalities. Several studies have reported the loss of retinal ganglion cells, reduced thickness of nerve fibre layers (NFL) and damage of the optic nerve head and fiber layers. These findings suggest a putative link between AD and visual function deficits. As genetic defects have been found to be associated with AD, it is possible to experimentally mimic this condition in animal models. AD gene mutations discovered in human amyloid pre- cursor protein (APP), presenilin 1/2 (PS1/PS2) and microtubule- associated tau protein have been used to engineer AD animal models. In this review, we discuss the underlying molecular mecha- nisms of AD in terms of amyloidogenesis and tauopathies, as well as explain the pathological changes leading to vision loss in AD patients. Subsequently, the biology of the genes/proteins which have a causative link to AD, including APP, PS1 and PS2 will be discussed. Several recent reports of retinal degeneration in AD transgenic mouse models are selected to examine the relationship between AD and visual disturbance. We believe that a well- established method to generate transgenic mice will enhance our understanding of AD pathology and its correlation with retinal degeneration, leading to possible detection and treatment methods for AD

Improving argumentative writing: Effects of a blended learning approach and gamification

This study investigated the effectiveness of a blended learning approach—involving the thesis, analysis, and synthesis key (TASK) procedural strategy; online Edmodo discussions; online message labels; and writing models—on student argumentative writing in a Hong Kong secondary school. It also examined whether the application of digital game mechanics increased student online contribution and writing performance. Three classes of Secondary 4 students (16- to 17-year-olds) participated in the 7-week study. The first experimental group (n = 22) utilized the blended learning + gamification approach. The second experimental group (n = 30) utilized only the blended learning approach. In the control group (n = 20), a teacher-led direct-instruction approach on the components of argumentation was employed. Data sources included students’ pre- and post-test written essays, students’ online Edmodo postings, and student and teacher interviews. We found a significant improvement in students’ writing using the blended learning approach. On-topic online contributions were significantly higher when gamification was adopted. Student and teacher opinions on the blended learning approach were also examined

Risk factors associated with brachial–ankle pulse wave velocity among peritoneal dialysis patients in Macao

BACKGROUND: Cardiovascular disease is the leading cause of mortality among peritoneal dialysis (PD) patients in Macao. Increased arterial stiffness determined by pulse wave velocity (PWV) has been established as an independent predictor of cardiovascular mortality in end-stage renal disease patients. The present study aims to investigate the relationship between arterial stiffness and its associated risk factors in chronic PD patients. METHODS: A total of 96 chronic PD patients (48 males/48 females) were included in the cross-sectional study. Arterial stiffness was assessed by brachial-ankle PWV (baPWV). Patients were divided into two subgroups according to mean baPWV value. On enrollment, clinical characteristics and biochemical parameters were collected. RESULTS: Compared with low baPWV group patients, high baPWV group patients were significant older (p<0.001) and more likely to have a high proportion of female gender (p=0.004) as well as previous CVD history (p=0.008). Serum albumin, pre-albumin levels and residual renal creatinine clearance (CCr) were significantly lower but the serum ferritin level was significantly higher in high baPWV group patients than in low baPWV group patients (all p<0.01). BaPWV was positively associated with age (r=0.534, p<0.001), Charlson comorbidity index (r=0.350, p<0.001) and serum ferritin level (r=0.340, p=0.001). Meanwhile, baPWV negatively correlated with serum albumin (r=−0.479, p<0.001), pre-albumin levels (r=−0.320, p=0.003) and residual renal CCr (r=−0.177, p=0.048). Age-adjusted partial correlation test found a significant correlation between baPWV and CRP (r=0.462, p<0.001). Multivariate regression analysis showed that baPWV was independently associated with age (p<0.001), serum albumin level (p=0.015), CRP (p=0.019) and residual renal CCr (p=0.045). CONCLUSION: Arterial stiffness, assessed by baPWV, had an independent correlation with age, serum albumin level, CRP level and residual renal CCr among PD patients in Macao