Significant Quality Degradation Research Articles

Optical Amplifier With Rotationally Symmetrical Pump Modes for Enhanced Mode Multiplexing

Multimode erbium-doped fiber amplifiers are promising candidates for the realization of cost- and energy-efficient long-haul transmission for mode-division multiplexing. Mode-dependent gain in such amplifiers is a potential source of signal quality degradation and should be avoided. We show by numerical simulations that gain values and noise figures for the signal modes exhibit an angular dependence if the amplifier is pumped with the LP21 mode. In order to avoid this angular dependence, we propose to use pump modes with a rotationally symmetric intensity distribution, such as the TE01 mode. Our simulation results show that pumping with this mode completely removes the angular dependence and optimizes gain and noise figure values for the signal modes.

Super Resolution for Multiview Images Using Depth Information

In stereoscopic and multiview video, binocular suppression theory states that the visual subjective quality of 3-D experience is not much affected by asymmetrical blurring of the individual views. Based on these studies, mixed-resolution frameworks applied for multiview systems offer great data-size reduction without incurring in significant quality degradation in 3-D video applications. However, it is interesting to recover high-frequency content of the blurred views, to reduce visual strain due to long-term exposure and to make the system suitable for free-viewpoint television. In this paper, we present a novel super-resolution technique, in which low-resolution views are enhanced with the aid of high-frequency content from neighboring full-resolution views, and the corresponding depth information for all views. Occlusions are handled by checking the consistency between views. Tests for synthetic and real image data in stereo and multiview cases are presented, and results show that significant objective quality gains can be achieved without any extra side information.

Fabrication and Optimization of a Conducting Polymer Sensor Array Using Stored Grain Model Volatiles

During storage, grain can experience significant degradation in quality due to a variety of physical, chemical, and biological interactions. Most commonly, these losses are associated with insects or fungi. Continuous monitoring and an ability to differentiate between sources of spoilage are critical for rapid and effective intervention to minimize deterioration or losses. Therefore, there is a keen interest in developing a straightforward, cost-effective, and efficient method for monitoring of stored grain. Sensor arrays are currently used for classifying liquors, perfumes, and the quality of food products by mimicking the mammalian olfactory system. The use of this technology for monitoring of stored grain and identification of the source of spoilage is a new application, which has the potential for broad impact. The main focus of the work described herein is on the fabrication and optimization of a carbon black (CB) polymer sensor array to monitor stored grain model volatiles associated with insect secretions (benzene derivatives) and fungi (aliphatic hydrocarbon derivatives). Various methods of statistical analysis (RSD, PCA, LDA, t test) were used to select polymers for the array that were optimum for distinguishing between important compound classes (quinones, alcohols) and to minimize the sensitivity for other parameters such as humidity. The performance of the developed sensor array was satisfactory to demonstrate identification and separation of stored grain model volatiles at ambient conditions.

Exploitation of data-information content in elastic-waveform inversions

Elastic-waveform inversions have the potential to provide detailed subsurface images of the elastic parameters (P- and S-wave velocities and density), but acquisition of suitable data sets and their inversion are nontrivial tasks. We explore the information content offered by elastic-waveform data by means of a 2D synthetic study. Comprehensive noise-free data sets that include recordings based on multicomponent (directed) sources and multicomponent (vector) receivers that fully surround the area of interest allow all elastic parameters to be reliably recovered. Results that are almost as good can be achieved with the more commonly used crosshole configuration. If only single-source components (e.g., those oriented perpendicular to the borehole walls) are used, then there is no significant quality degradation of the tomographic images. Crosshole experiments that include pressure sources and multicomponent receivers still allow P- and S-wave velocities to be recovered, but such data sets contain virtually no information about the density. Finally, seismic data collected with omnidirectional pressure sources and pressure receivers contain information about P- and S-wave velocities, but there are pronounced trade-offs between these parameters. This is demonstrated through formal model-resolution analyses. This study concludes that seismic data recorded with pressure sources and 2C receivers offer the best compromise between acquisition efficiency and data-information content.

Artifact Removal in Physiological Signals—Practices and Possibilities

The combination of reducing birth rate and increasing life expectancy continues to drive the demographic shift toward an aging population. This, in turn, places an ever-increasing burden on healthcare due to the increasing prevalence of patients with chronic illnesses and the reducing income-generating population base needed to sustain them. The need to urgently address this healthcare "time bomb" has accelerated the growth in ubiquitous, pervasive, distributed healthcare technologies. The current move from hospital-centric healthcare toward in-home health assessment is aimed at alleviating the burden on healthcare professionals, the health care system and caregivers. This shift will also further increase the comfort for the patient. Advances in signal acquisition, data storage and communication provide for the collection of reliable and useful in-home physiological data. Artifacts, arising from environmental, experimental and physiological factors, degrade signal quality and render the affected part of the signal useless. The magnitude and frequency of these artifacts significantly increases when data collection is moved from the clinic into the home. Signal processing advances have brought about significant improvement in artifact removal over the past few years. This paper reviews the physiological signals most likely to be recorded in the home, documenting the artifacts which occur most frequently and which have the largest degrading effect. A detailed analysis of current artifact removal techniques will then be presented. An evaluation of the advantages and disadvantages of each of the proposed artifact detection and removal techniques, with particular application to the personal healthcare domain, is provided.

Electrode Failure: Tissue, Electrical, and Material Responses

The development of invasive, rehabilitative neuroprosthetics for humans requires reliable neural probes that are capable of recording large ensembles of neurons for a long period of time. Recent advances in the development of neuroprosthetics in animals and humans have shown that communication and control can be directly derived from the central nervous system (CNS) for restoring lost motor ability. This proof of concept has opened the possibility of new therapies for the millions of individuals suffering from neurological disorders of the nervous system. The success of these therapies hinges on the ability to reliably access the relevant signals from the brain with high quality for the lifetime of the patient. As a result, research has focused on the cascade of events that follow chronic implantation of microelectrodes and temporal degradation in the signal and electrode quality: signal-to-noise ratio, noise floor, peak amplitude, and neuronal yield. Implanted microelectrodes have been reported to suffer from time-dependent degradation in signal quality due to unknown issues related to tissue interfaces.

Industrial-scale radio frequency treatments for insect control in lentils

Radio frequency (RF) treatments are considered to be a potential postharvest technology for disinfesting legumes of internal seed pests such as the cowpea weevil. After treatment protocols are shown to control postharvest insects without significant quality degradation, it is important to scale-up laboratory RF treatments to industrial level applications. A 27.12 MHz, 6 kW RF unit with a built-in forced hot air system was used to conduct industrial scale-up studies. A treatment protocol was designed to provide 100% cowpea weevil mortality combined RF with forced hot air to heat product to 60 °C for 10 min, followed by forced ambient air cooling for 20 min. An electrode gap (14.0 cm) was chosen based on the electric current and heating time, and conveyor belt speed was set to 7.5 m/h. Heating uniformity was evaluated by measuring post-treatment surface temperatures with a thermal image camera and interior temperatures with thermocouples. Changes in moisture content, color and germination were used to evaluate treatment effects on product quality. Finally, the RF system heating efficiency and throughput were calculated. Results showed that heating uniformity and quality of lentils in continuous RF treatment with hot air and movement were acceptable, the average heating efficiency of the RF system was 76.5% and throughput was 208.7 kg/h. The average energy efficiency and throughput of the RF system provided sufficient data to develop an industrial-scale RF process as an alternative to chemical fumigation.

Distribution of benthic communities affected by human activities in the west coast of Alexandria, Mediterranean Sea, Egypt

In the framework of marine ecosystem evaluation, this study was carried out where sediment microorganisms were collected bimonthly from 16 sites over one year in the western coast of Alexandria. This area comprises different human activities (urban sewage, agriculture irrigation, industrial wastes, petroleum spill, tourist stress, fishing and commercial navigation). Macrobenthos communities are well indicators of water and sediment quality. Bottom invertebrate’s diversity, comparison of benthos communities at different sampling sites and the biomass were determined as well as the numerical abundance of benthos in comparison to the different environmental parameters. Discharging of chemical pollutants in coastal waters leads to significant degradation in the water quality that altered the macro invertebrates’ diversity indices. The most western sites are less stressed area indicating low diversity rather than the stressed area close to the main sources of pollutants discharge that has relatively high pollution and generally with good diversity. The benthic communities are dominated by few species of pollution tolerance which are used as indicators of polluted sediments such as free-living nematodes and polychaetes. The regional distribution of benthic invertebrate’s communities varied at different sites and over the period of collections that total abundance ranged from 959 to 8444 ind./m 2 with an annual average of 3072 ind./m 2 and seven benthos groups can be sequenced as follows: Nematodes 46% > polychaetes 22% > amphipods 13.8% >cirripedes 4.8% > oligochaetes 4% > gastropods 3.0% > bivalves 1.5%. On the other hand, biomass of benthic structure has an annual average of 155 g/m 2 , where six predomination benthic groups can be ranked in the following sequence: Cirripedes 33.5% > Algae 30.6% > Gastropods 12.7% > Bivalves 9.1% > Sea grass 7.0% > Polychaetes 1.7%. At the different sites, the general structure of species number of benthos groups indicated that Polychaeta was the most common group comprising 27 species of 80 the total number of taxa. The values of species diversity (H`) had relatively moderate diversity (1.3 – 2.02) at most stations and in general the decline in diversity is primarily attributed to the uneven distribution of individuals among the species. On the other hand, the species diversity was only 1.6 at Site 2 though it was the richest that may be attributed to the number of species. Values of the evenness index indicated that sites 1, 8, 9, 10 were highly diverse in benthic communities. The Swartz’s dominance index value indicated less stress with high diversity and number of species. The area located close to the outfall of the two main drains are characterized by having distinct eutrophication level leading to significant increase in the species richness and mean abundance of benthic communities of the tolerant species. Continuous monitoring and assessing of macrobenthic communities is needed to determine the short and long-term changes in the marine ecosystem that are essential for fisheries management along the coastal region.

Subjective Quality Evaluation of Foveated Video Coding Using Audio-Visual Focus of Attention

This paper presents a foveated coding method using audio-visual focus of attention and its evaluation through extensive subjective experiments on both standard-definition and high-definition sequences. Regarding a sound-emitting region as the location drawing the human attention, the method applies varying quality levels in an image frame according to the distance of a pixel to the identified sound source. Two experiments are presented to prove the efficiency of the method. Experiment 1 examines the validity and effectiveness of the method in comparison to the constant quality coding for high-quality conditions. In Experiment 2, the method is compared to the fixed bit rate coding for low quality conditions where coding artifacts are noticeable. The results demonstrate that the foveated coding method provides considerable coding gain without significant quality degradation, but uneven distributions of the coding artifacts (blockiness) by the method are often less preferred than the uniform distribution of the artifacts. Additional interesting findings are also discussed, such as content dependence of the performance of the method, the memory effect in multiple viewings, and the difference in the quality perception for frame size variations.

Robust decoder-based error control strategy for recovery of H.264/AVC video content

Real-time wireless conversational and broadcasting multimedia applications offer particular transmission challenges as reliable content delivery cannot be guaranteed. The undelivered and erroneous content causes significant degradation in quality of experience. The H.264/AVC standard includes several error resilient tools to mitigate this effect on video quality. However, the methods implemented by the standard are based on a packet-loss scenario, where corrupted slices are dropped and the lost information concealed. Partially damaged slices still contain valuable information that can be used to enhance the quality of the recovered video. This study presents a novel error recovery solution that relies on a joint source-channel decoder to recover only feasible slices. A major advantage of this decoder-based strategy is that it grants additional robustness while keeping the same transmission data rate. Simulation results show that the proposed approach manages to completely recover 30.79% of the corrupted slices. This provides frame-by-frame peak signal-to-noise ratio (PSNR) gains of up to 18.1 dB, a result which, to the knowledge of the authors, is superior to all other joint source-channel decoding methods found in literature. Furthermore, this error resilient strategy can be combined with other error resilient tools adopted by the standard to enhance their performance.

Multiple passive element enriched photoacoustic computed tomography

Recently, we presented a method using laser-induced ultrasound from an external absorber (passive element) to image the ultrasound transmission parameters of an object under photoacoustic tomographic investigation. The method suffers from long measurement times due to the requirement for a large number of views and consequently physical projections around the object. Here we propose and validate an approach that permits a multitude of views to be obtained within a limited projection scenario. The approach uses a plurality of spatially distributed external absorbers in the path of the light, that results in multiple laser-induced ultrasound sources to interrogate the object from a number of angles. This reduces the required number of rotation angles or physical projections around the object, permitting a considerable reduction in imaging time without significant degradation in image quality. The approach brings the concept of hybrid imaging of ultrasound transmission parameters together with photoacoustic imaging, into the realm of practical application.

On the Dimensioning of WDM Optical Networks With Impairment-Aware Regeneration

Although the problem of dimensioning an optical transport network is not new, the consideration of signal quality degradation caused by the optical medium calls for revisiting the problem in the context of dimensioning optical wavelength division multiplexing (WDM) networks. This paper addresses the issue of minimum-cost planning of long-reach WDM networks in combination with optoelectronic signal regeneration as a countermeasure for sanitizing the signal quality of lightpaths that are found to be impaired. The commonly used method of placing regenerators proportionally to the physical distance covered by a lightpath is evaluated in a realistic dimensioning scenario and for various heterogeneity degrees of optical equipment, showing that it is plagued with a serious tradeoff between efficacy and cost of regeneration. As a remedy, we propose a novel method for design/dimensioning and regeneration placement for WDM networks that employs impairment-awareness. Through experimentation with real optical network configurations and for varying heterogeneity of optical equipment, the proposed method is shown to break the aforementioned tradeoff, resulting in significant reduction in regeneration effort compared to distance-based regeneration. This is achieved without compromising the signal quality of any of the lightpaths selected by the dimensioning process and with increased cost efficiency.

Modeling approach to treatability analyses of an existing treatment plant

To comply with the Stage 1 and 2 Disinfectants/Disinfection Byproducts Rules, utilities have modified or changed their treatment processes, based typically on historical water quality. However, when there has been a significant degradation in source water quality, it has been a struggle to maintain compliance at many plants. The objective of this study was to develop long‐term planning tools to determine the potential effect of source water quality changes on the ability of existing treatment facilities to continue to comply with current and anticipated disinfection by‐product standards. These studies also evaluated the maximum concentrations for combinations of influent total organic carbon and bromide that the existing facilities could effectively handle and treatment costs under a worst‐case scenario. The planning tools were developed based on actual water quality and full‐scale operational data from the Metropolitan Water District of Southern California's water treatment plants. The tool was originally developed in 2007 and was calibrated and validated with newly available data in 2009.

Dynamic assignment of neural resources in auditory comprehension of complex sentences

Under real-life adverse listening conditions, the interdependence of the brain's analysis of language structure (syntax) and its analysis of the acoustic signal is unclear. In two fMRI experiments, we first tested the functional neural organization when listening to increasingly complex syntax in fMRI. We then tested parametric combinations of syntactic complexity (argument scrambling in three degrees) with speech signal degradation (noise-band vocoding in three different numbers of bands), to shed light on the mutual dependency of sound and syntax analysis along the neural processing pathways. The left anterior and the posterior superior temporal sulcus (STS) as well as the left inferior frontal cortex (IFG) were linearly more activated as syntactic complexity increased (Experiment 1). In Experiment 2, when syntactic complexity was combined with improving signal quality, this pattern was replicated. However, when syntactic complexity was additive to degrading signal quality, the syntactic complexity effect in the IFG shifted dorsally and medially, and the activation effect in the left posterior STS shifted from posterior toward more middle sections of the sulcus. A distribution analysis of supra- as well as subthreshold data was indicative of this pattern of shifts in the anterior and posterior STS and within the IFG. Results suggest a signal quality gradient within the fronto-temporal language network. More signal-bound processing areas, lower in the processing hierarchy, become relatively more recruited for the analysis of complex language input under more challenging acoustic conditions (“upstream delegation”). This finding provides evidence for dynamic resource assignments along the neural pathways in auditory language comprehension.

Coherent beam combination of narrow-linewidth 15μm fiber amplifiers in a long-pulse regime

We report what we believe to be the first experimental demonstration of coherent beam combining of two fiber amplifiers in a 100 ns pulse regime using a signal leak between the pulses. Pulses of ∼100 W stimulated-Brillouin-scattering limited peak power are combined with 95% efficiency, a residual phase error of λ/27, and no significant beam quality degradation.

A Combined Scheme for Controlling GSM Network Calls Congestion

Network congestion and signal quality degradation are the major problems of the Global System for Mobile communication (GSM) most especially as the number of customers increases. They are issues that constantly and continuously demand for further researches to improve network performance. Congestion in various systems has always been tackled with various attempts, all of which falls in either the congestion avoidance category or congestion management category. Congestion avoidance has however been adjudged the best scheme for controlling network congestion and this is the approach employed in this research work. The conventional GSM network calls congestion control methods such as Token Bank, Auto atic Call Gapping among which Call Admission Control (CAC) is the best, was selected for this work. Dynamic load balancing technique was combined with CAC to re-route calls that would have been dropped to another less busy cell within the Base Station Controller (BSC) area. A naive form of Dijkstra shortest path algorithm was used to find the shortest route to which calls can be transferred among the collocated base station cells. The combined algorithms were implemented on JAVA platform using real life call data record (CDR) collected from Globacom Nigeria Limited New Call Blocking and Handoff Call Dropping Probabilities (NCBP and HCDP) were used to measure the performance results. The two probabilities were computed for both CAC only and the combined scheme. The results obtained showed that there is significant reduction in the values of both NCBP and HCDP by 71.43% and 100% respectively, of cells considered for the new combined scheme when compared with that of the CAC only. This indicates that the new scheme has further reduced the values of the NCBP and HCDP which enabled the cells to accommodate more calls thereby increasing the efficiency of the network performance.

Quantifying the decrease of the photovoltaic panels’ energy yield due to phenomena of natural air pollution disposal

Photovoltaic (PV) applications, gaining worldwide interest during the last years, comprise a promising renewable energy based solution, able to considerably contribute to the constantly increasing energy demand of our planet. Currently, residential applications possess a considerable share of the global PV market since fiscal and practical incentives have reinforced their promotion. On the other hand, high population concentration, rapid industrialisation and economic development of urban areas all over the world have caused significant degradation of the urban air quality. In this context, the actual performance of five identical pairs of roof-top PV-panels, operating in the aggravated urban environment of Athens (from the atmospheric air pollution point of view), is currently evaluated. For this purpose, a series of systematic experimental measurements is conducted within a certain time period and the influence of different dust deposition densities on the energy yield and the economic performance of the small power station is estimated. According to the results obtained, the presence of dust considerably affects the PV-panels’ performance since even a relatively small dust deposition density (≈1 g/m2) may result in remarkable energy losses corresponding almost to 40 €/kWp on an annual basis.

Musculoskeletal disorders in dumper operators exposed to whole body vibration at Indian mines

Dumper operators are exposed to whole body vibration (WBV) in the course of their work. The exposure to WBV in a coal mine in Central India was investigated through measurement of the magnitude of vibration and exposure time. The vibration magnitude along the dominant Z-axis ranged from 0.644 to 1.82 m/s2 in terms of root mean square acceleration. When evaluated in conjunction with their average daily exposure time of 5 h, all dumpers caused elevated health risk for their operators according to guidelines in ISO 2631-1:1997 WBV standard. Health risks were re-affirmed when vibration dose value (VDV) was applied as an additional tool for risk assessment. Forty dumper operators and 20 controls from the same mine were selected for detailed studies. The control population was not exposed to WBV. An epidemiological study was carried out to determine the prevalence of musculoskeletal disorders (MSD) related to WBV exposure. It was observed that the problem of low back pain was significantly higher (85%) in the exposed population as compared to controls (20%). Similarly, pain in the ankle (37.83%), shoulder (30%) and neck (37.5%) was higher among exposed personnel as compared to the control population (5, 0 and 15%, respectively). A significant degradation in quality of life among the exposed subjects was also observed.

System-Level Energy Optimization for Error-Tolerant Image Compression

Based on the natural error tolerance of image and multimedia processing, aggressive voltage scaling has been considered for energy savings by trading off accuracy. However, aggressive voltage scaling in image compression may not reduce overall system energy consumption because of the reduction in the compression ratio. Based on the system-level analysis, we present an adaptive pixel and coefficient truncation technique to successfully reduce error rates so that we can achieve great energy savings without significant quality degradation. Our experimental results show that average energy savings of up to 40% can be realized at a trivial implementation cost.

Voice Conversion Based on Weighted Frequency Warping

Any modification applied to speech signals has an impact on their perceptual quality. In particular, voice conversion to modify a source voice so that it is perceived as a specific target voice involves prosodic and spectral transformations that produce significant quality degradation. Choosing among the current voice conversion methods represents a trade-off between the similarity of the converted voice to the target voice and the quality of the resulting converted speech, both rated by listeners. This paper presents a new voice conversion method termed Weighted Frequency Warping that has a good balance between similarity and quality. This method uses a time-varying piecewise-linear frequency warping function and an energy correction filter, and it combines typical probabilistic techniques and frequency warping transformations. Compared to standard probabilistic systems, Weighted Frequency Warping results in a significant increase in quality scores, whereas the conversion scores remain almost unaltered. This paper carefully discusses the theoretical aspects of the method and the details of its implementation, and the results of an international evaluation of the new system are also included.