Wavelet transform - artificial neural network receiver with adaptive equalisation for a diffuse indoor optical wireless OOK link

This paper presents an alternative approach for signal detection and equalization using the continuous wavelet transform (CWT) and the artificial neural network (ANN) in diffuse indoor optical wireless links (OWL). The wavelet analysis is used for signal preprocessing (feature extraction) and the ANN for signal detection. Traditional receiver architectures based on matched filter (MF) experience significant performance degradation in the presence of artificial light interference (ALI) and multipath induced intersymbol interference (ISI). The proposed receiver structure reduces the effect of ALI and ISI by selecting a particular scale of CWT that corresponds to the desired signal and classifying the signal into binary 1 and 0 based on an observation vector. By selecting particular scales corresponding to the signal, the effect of ALI is reduced. We show that there is little variation when using 30 and 5 neurons in the first layer, with one layer ANN model showing a consistently worse BER performance than other models, whilst the 15 neuron model show some behaviour anomalies from a BER of approximately 10-3. The simulation results show that the Wavelet-ANN architecture outperforms the traditional MF based receiver even with the filter is matched to the ISI affected pulse shape. The Wavelet-ANN receiver is also capable of providing a bit error rate (BER) performance comparable to the equalized forms of traditional receiver structure

Wavelet analysis and artificial intelligence for diffuse indoor optical wireless communications

This thesis investigates the use of Wavelet Analysis and Artificial Intelligence as elements of a diffuse indoor infrared (IR) optical wireless communications receiver. The work presented employs MatlabTM enabled simulations to explore the effects of inter symbol interference (ISI) and fluorescent light interference on a receiver using these techniques. The results are compared with those obtained from traditional receiver architectures. IR devices have been commonplace in most households as remote control handsets for domestic entertainment equipment for many years. More recently, IR communication systems have been deployed in mobile phones, laptop computers and computer peripheral devices largely for the purpose of short range point-to-point data transfers. Since the late 1970's there has been consistent interest and research in the use of the IR part of the spectrum for short-range Wireless Local Area Networks (WLAN). IR offers a number of potential advantages over radio frequency systems such as unregulated and re-usable bandwidth, inherent security, resistance to multipath fading and the availability of mass produced, low cost emitters and detectors. However, significant problems still persist to impede the widespread and popular deployment of IR enabled LANs. The work presented in this thesis focuses on the use of the largely software enabled techniques of Wavelet Analysis and Artificial Intelligence (Wavelet-AI) as novel alternatives to mitigating the difficulties associated with diffuse indoor IR communication systems. Indoor IR wireless links usually have to operate in the presence of intense noise generated by ambient light sources. The source can be natural sunlight from doors and windows, or artificial light from incandescent and fluorescent fittings. In addition to contributing to the generation of shot noise, artificial light sources can also impose a periodic interference signal that can significantly impair the performance of an optical link. Electrical high pass filtering is a typical mitigating technique that is effective at reducing the interference signal. Unfortunately it also introduces a performance degrading phenomenon known as baseline wander. Using well established interferer models the results of original Wavelet-AI inclusive simulations are presented and compared with those of typical receiver architectures with and without electrical high pass filtering. The performance of Wavelet-AI based receiver was found to be superior to traditional unfiltered receiver architecture in the presence of artificial light interference. At low to medium data rates the Wavelet-AI receiver was also found to outperform all but one case of the traditional receiver architecture employing electrical high pass filtering. The results of baseline wander simulations with On-and-Off keying (00K) modulation and the Wavelet-Al receiver architectures is presented and shows that the Wavelet-AI architecture is far more tolerant to baseline wander. In diffuse or non-directed links multipath propagation induced ISI can impose a significant performance penalty for data rates above approximately 10 Mb/s. Typical compensation techniques include the use of equalisers such as the zero-forcing equaliser (ZFE), the minimum mean square equaliser (MMSE) and the decision feedback equaliser (DFE), usually implemented as digital filters. The results of original Wavelet-Al inclusive simulations are presented and compared with those of typical receiver architectures with and without filtering and equalisers. In all cases the simulation results show that the Wavelet-Al receiver architecture performance is superior to the non-equalised traditional receiver. The Wavelet-AI receiver results show a very similar performance to the equalised traditional OOK receiver and the equalised Level 4 Pulse Position Modulation (4-PPM) receiver. However, between a 2 dB and 4 dB optical power penalty was incurred for the 8-PPM Wavelet-AI case. This result may not..

Tuition, 18 October 1842

https://egrove.olemiss.edu/aldrichcorr_b/1044/thumbnail.jp

Wavelet analysis and artificial intelligence for diffuse indoor optical wireless communications

This thesis investigates the use of Wavelet Analysis and Artificial Intelligence as elements of a diffuse indoor infrared (IR) optical wireless communications receiver. The work presented employs MatlabTM enabled simulations to explore the effects of inter symbol interference (ISI) and fluorescent light interference on a receiver using these techniques. The results are compared with those obtained from traditional receiver architectures. IR devices have been commonplace in most households as remote control handsets for domestic entertainment equipment for many years. More recently, IR communication systems have been deployed in mobile phones, laptop computers and computer peripheral devices largely for the purpose of short range point-to-point data transfers. Since the late 1970's there has been consistent interest and research in the use of the IR part of the spectrum for short-range Wireless Local Area Networks (WLAN). IR offers a number of potential advantages over radio frequency systems such as unregulated and re-usable bandwidth, inherent security, resistance to multipath fading and the availability of mass produced, low cost emitters and detectors. However, significant problems still persist to impede the widespread and popular deployment of IR enabled LANs. The work presented in this thesis focuses on the use of the largely software enabled techniques of Wavelet Analysis and Artificial Intelligence (Wavelet-AI) as novel alternatives to mitigating the difficulties associated with diffuse indoor IR communication systems. Indoor IR wireless links usually have to operate in the presence of intense noise generated by ambient light sources. The source can be natural sunlight from doors and windows, or artificial light from incandescent and fluorescent fittings. In addition to contributing to the generation of shot noise, artificial light sources can also impose a periodic interference signal that can significantly impair the performance of an optical link. Electrical high pass filtering is a typical mitigating technique that is effective at reducing the interference signal. Unfortunately it also introduces a performance degrading phenomenon known as baseline wander. Using well established interferer models the results of original Wavelet-AI inclusive simulations are presented and compared with those of typical receiver architectures with and without electrical high pass filtering. The performance of Wavelet-AI based receiver was found to be superior to traditional unfiltered receiver architecture in the presence of artificial light interference. At low to medium data rates the Wavelet-AI receiver was also found to outperform all but one case of the traditional receiver architecture employing electrical high pass filtering. The results of baseline wander simulations with On-and-Off keying (00K) modulation and the Wavelet-Al receiver architectures is presented and shows that the Wavelet-AI architecture is far more tolerant to baseline wander. In diffuse or non-directed links multipath propagation induced ISI can impose a significant performance penalty for data rates above approximately 10 Mb/s. Typical compensation techniques include the use of equalisers such as the zero-forcing equaliser (ZFE), the minimum mean square equaliser (MMSE) and the decision feedback equaliser (DFE), usually implemented as digital filters. The results of original Wavelet-Al inclusive simulations are presented and compared with those of typical receiver architectures with and without filtering and equalisers. In all cases the simulation results show that the Wavelet-Al receiver architecture performance is superior to the non-equalised traditional receiver. The Wavelet-AI receiver results show a very similar performance to the equalised traditional OOK receiver and the equalised Level 4 Pulse Position Modulation (4-PPM) receiver. However, between a 2 dB and 4 dB optical power penalty was incurred for the 8-PPM Wavelet-AI case.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Characterization of power induced heating and damage in fiber optic probes for near-field scanning optical microscopy

This is the published version, also available here: http://dx.doi.org/10.1063/1.2740133.Tip-induced sample heating in near-field scanning optical microscopy (NSOM) is studied for fiber optic probes fabricated using the chemical etching technique. To characterize sample heating from etched NSOM probes, the spectra of a thermochromic polymer sample are measured as a function of probe output power, as was previously reported for pulled NSOM probes. The results reveal that sample heating increases rapidly to ∼55–60°C as output powers reach ∼50nW. At higher output powers, the sample heating remains approximately constant up to the maximum power studied of ∼450nW. The sample heating profiles measured for etched NSOM probes are consistent with those previously measured for NSOM probes fabricated using the pulling method. At high powers, both pulled and etched NSOM probes fail as the aluminumcoating is damaged. For probes fabricated in our laboratory we find failure occurring at input powers of 3.4±1.7 and 20.7±6.9mW for pulled and etched probes, respectively. The larger half-cone angle for etched probes (∼15° for etched and ∼6° for pulled probes) enables more light delivery and also apparently leads to a different failure mechanism. For pulled NSOM probes, high resolution images of NSOM probes as power is increased reveal the development of stress fractures in the coating at a taper diameter of ∼6μm. These stress fractures, arising from the differential heating expansion of the dielectric and the metalcoating, eventually lead to coating removal and probe failure. For etched tips, the absence of clear stress fractures and the pooled morphology of the damaged aluminumcoating following failure suggest that thermal damage may cause coating failure, although other mechanisms cannot be ruled out

Propulsion Systems Panel

Topics addressed are: (1) cryogenic tankage; (2) launch vehicle TPS/insulation; (3) durable passive thermal control devices and/or coatings; (4) development and characterization of processing methods to reduce anisotropy of material properties in Al-Li; (5) durable thermal protection system (TPS); (6) unpressurized Al-Li structures (interstages, thrust structures); (7) near net shape sections; (8) pressurized structures; (9) welding and joining; (10) micrometeoroid and debris hypervelocity shields; (11) state-of-the-art shell buckling structure optimizer program to serve as a rapid design tool; (12) test philosophy; (13) reduced load cycle time; (14) structural analysis methods; (15) optimization of structural criteria; and (16) develop an engineering approach to properly trade material and structural concepts selection, fabrication, facilities, and cost

Hip morphology in elite golfers : asymmetry between lead and trail hips

Aim: During a golf swing, the lead hip (left hip in a right-handed player) rotates rapidly from external to internal rotation, while the opposite occurs in the trail hip. This study assessed the morphology and pathology of golfers’ hips comparing lead and trail hips. Methods: A cohort of elite golfers were invited to undergo MRI of their hips. Hip morphology was evaluated by measuring acetabular depth (pincer shape=negative measure), femoral neck antetorsion (retrotorsion=negative measure) and α angles (cam morphology defined as α angle >55° anteriorly) around the axis of the femoral neck. Consultant musculoskeletal radiologists determined the presence of intra-articular pathology. Results: 55 players (mean age 28 years, 52 left hip lead) underwent MRI. No player had pincer morphology, 2 (3.6%) had femoral retrotorsion and 9 (16%) had cam morphology. 7 trail hips and 2 lead hips had cam morphology (p=0.026). Lead hip femoral neck antetorsion was 16.7° compared with 13.0° in the trail hip (p<0.001). The α angles around the femoral neck were significantly lower in the lead compared with trail hips (p<0.001), with the greatest difference noted in the anterosuperior portion of the head neck junction; 53° vs 58° (p<0.001) and 43° vs 47° (p<0.001). 37% of trail and 16% of lead hips (p=0.038) had labral tears. Conclusions: Golfers’ lead and trail hips have different morphology. This is the first time side-to-side asymmetry of cam prevalence has been reported. The trail hip exhibited a higher prevalence of labral tears

Moderators, Mediators, and Prognostic Indicators of Treatment With Hip Arthroscopy or Physical Therapy for Femoroacetabular Impingement Syndrome: Secondary Analyses From the Australian FASHIoN Trial.

BACKGROUND Although randomized controlled trials comparing hip arthroscopy with physical therapy for the treatment of femoroacetabular impingement (FAI) syndrome have emerged, no studies have investigated potential moderators or mediators of change in hip-related quality of life. PURPOSE To explore potential moderators, mediators, and prognostic indicators of the effect of hip arthroscopy and physical therapy on change in 33-item international Hip Outcome Tool (iHOT-33) score for FAI syndrome. STUDY DESIGN Cohort study; Level of evidence, 2. METHODS Overall, 99 participants were recruited from the clinics of orthopaedic surgeons and randomly allocated to treatment with hip arthroscopy or physical therapy. Change in iHOT-33 score from baseline to 12 months was the dependent outcome for analyses of moderators, mediators, and prognostic indicators. Variables investigated as potential moderators/prognostic indicators were demographic variables, symptom duration, alpha angle, lateral center-edge angle (LCEA), Hip Osteoarthritis MRI Scoring System (HOAMS) for selected magnetic resonance imaging (MRI) features, and delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) score. Potential mediators investigated were change in chosen bony morphology measures, HOAMS, and dGEMRIC score from baseline to 12 months. For hip arthroscopy, intraoperative procedures performed (femoral ostectomy ± acetabular ostectomy ± labral repair ± ligamentum teres debridement) and quality of surgery graded by a blinded surgical review panel were investigated for potential association with iHOT-33 change. For physical therapy, fidelity to the physical therapy program was investigated for potential association with iHOT-33 change. RESULTS A total of 81 participants were included in the final moderator/prognostic indicator analysis and 85 participants in the final mediator analysis after exclusion of those with missing data. No significant moderators or mediators of change in iHOT-33 score from baseline to 12 months were identified. Patients with smaller baseline LCEA (β = -0.82; P = .034), access to private health care (β = 12.91; P = .013), and worse baseline iHOT-33 score (β = -0.48; P < .001) had greater iHOT-33 improvement from baseline to 12 months, irrespective of treatment allocation, and thus were prognostic indicators of treatment response. Unsatisfactory treatment fidelity was associated with worse treatment response (β = -24.27; P = .013) for physical therapy. The quality of surgery and procedures performed were not associated with iHOT-33 change for hip arthroscopy (P = .460-.665 and P = .096-.824, respectively). CONCLUSION No moderators or mediators of change in hip-related quality of life were identified for treatment of FAI syndrome with hip arthroscopy or physical therapy in these exploratory analyses. Patients who accessed the Australian private health care system, had smaller LCEAs, and had worse baseline iHOT-33 scores, experienced greater iHOT-33 improvement, irrespective of treatment allocation

Neuropathic pain

Neuropathic pain is caused by a lesion or disease of the somatosensory system, including peripheral fibres (Aβ, Aδ and C fibres) and central neurons, and affects 7-10% of the general population. Multiple causes of neuropathic pain have been described and its incidence is likely to increase owing to the ageing global population, increased incidence of diabetes mellitus and improved survival from cancer after chemotherapy. Indeed, imbalances between excitatory and inhibitory somatosensory signalling, alterations in ion channels and variability in the way that pain messages are modulated in the central nervous system all have been implicated in neuropathic pain. The burden of chronic neuropathic pain seems to be related to the complexity of neuropathic symptoms, poor outcomes and difficult treatment decisions. Importantly, quality of life is impaired in patients with neuropathic pain owing to increased drug prescriptions and visits to health care providers, as well as the morbidity from the pain itself and the inciting disease. Despite challenges, progress in the understanding of the pathophysiology of neuropathic pain is spurring the development of new diagnostic procedures and personalized interventions, which emphasize the need for a multidisciplinary approach to the management of neuropathic pain