Image Reconstruction for Multi-frequency Electromagnetic Tomography based on Multiple Measurement Vector Model

Imaging the bio-impedance distribution of a biological sample can provide understandings about the sample's electrical properties which is an important indicator of physiological status. This paper presents a multi-frequency electromagnetic tomography (mfEMT) technique for biomedical imaging. The system consists of 8 channels of gradiometer coils with adjustable sensitivity and excitation frequency. To exploit the frequency correlation among each measurement, we reconstruct multiple frequency data simultaneously based on the Multiple Measurement Vector (MMV) model. The MMV problem is solved by using a sparse Bayesian learning method that is especially effective for sparse distribution. Both simulations and experiments have been conducted to verify the performance of the method. Results show that by taking advantage of multiple measurements, the proposed method is more robust to noisy data for ill-posed problems compared to the commonly used single measurement vector model.Comment: This is an accepted paper which has been submitted to I2MTC 2020 on Nov. 201

Investigation on gas migration in saturated materials with low permeability

International audienceInvestigation of the hydro-mechanical effects on gas migration in saturated materials with low permeabilityis of great theoretical and practical significances in many engineering fields. The conventional two-phaseflow (visco-capillary flow) theory, which regards the capillary pressure as the only controlling factor in gasmigration processes, is commonly adopted to describe the gas flow in geo-materials. However, formaterialswith lowpermeability, the conventional two-phase flow theory cannot properly describe the gasmigration.In this work, hydro-mechanical coupled gas injection tests were conducted. The volumetric variation of theliquid for applying the confining pressure in the specimen cell and the gas flow rate were monitored. Testresults indicate that gas migration is influenced by the capillary pressure and the mechanical stress simultaneously.The two key parameters of the gas entry pressure Pentry and the gas induced-dilatancy pressurePdilatancy are introduced for description of gas migration with respect to the capillary pressure and the mechanicalstress effects, respectively. When the gas injection pressure is smaller than the Pentry and thePdilatancy, the balance between the gas injection pressure and the confining pressure will lead to an intermittentgas flow. Sudden increase of gas flow rate could be observed once the gas injection pressure approachesthe Pentry or the Pdilatancy. For higher gas injection pressures, the mechanical stress effects on gas migrationcould not be neglected. The sudden increase of gas flux under high gas injection pressures could be causedby the mechanical induced-dilatancy of channels, capillary pressure induced-continuous flow pathways, aswell as the failure of sealing-efficiency. The failure of sealing-efficiency is closely related to the differencebetween the gas injection pressure and the confining pressure rather than the properties of the materialtested. Monitoring the volume of liquid for applying confining pressure is helpful for detecting the failureof sealing efficiency and the mechanism of gas breakthrough

Community Attachment and Environmental Stewardship: A Peri-Urban Perspective

This Chapter questions the negligence of attachment scholarship in the context of environmental stewardship with a specific focus in peri-urban areas. This Chapter has illuminated the imperatives of considering place attachement as an important factor in realizing environment stewardship in peri-urban areas. Three selected hamlets (Nzasa, Kisarawe and Pugu-Kibaoni) constitute the study area. A standard closed-ended questionnaire for assessing the extent of attachment of the community was deployed. Literature review on the other hand was used to map baseline information of the study area including the historical significance of the Pugu and Kazimzumbwi forest reserves. Three attachment attributes were explored;, community knowlegiability levels of the area; level of thoughts and feelings of the area; and the extent of community connection to natural resources in the area. It was revealed that the extent of community connection to the forest reserves are relatively strong. The study revealed considerable contrast on forest knowledgiability levels among men and women in the Pugu and Kazimzumbwi forest reserves. Males are generally revealed to be more knowledgiable of the Pugu and Kazimzumbwi forest reserves as compared to their female counterparts. The study revealed that there was substantial relationship between residence status and the level of thoughts and feelings on the forest reserves. The study has shown that natives have more thoughts and feelings of the present and the future of the forest reserves as compared to those who migrated from other parts of the country. The findings suggest that community attachment is of considerable importance in influencing environmental behavior either positively or negatively. Whilist the empirical evidence are drawn from the peri-urban areas of Pugu and Kazimzumbwi forest reserves of Dar es Salaam city, the message thereoff is representing a broad reality in the peri-urban areas of the Global South. The inclusion of community attachment perspective in negotiating environmental stewardship is advocated for as it might contribute in addressing the growing degradation of natural resources in peri-urban areas which has been increasingly declining

Morphology, photosynthetic physiology and biochemistry of nine herbaceous plants under water stress

Global climate warming and shifts in rainfall patterns are expected to trigger increases in the frequency and magnitude of drought and/or waterlogging stress in plants. To cope with water stress, plants develop diverse tactics. However, the adoption capability and mechanism vary depending upon the plant species identity as well as stress duration and intensity. The objectives of this study were to evaluate the species-dependent responses of alpine herbaceous species to water stress. Nine herbaceous species were subjected to different water stresses (including moderate drought and moderate waterlogging) in pot culture using a randomized complete block design with three replications for each treatment. We hypothesized that water stress would negatively impact plant growth and metabolism. We found considerable interspecies differences in morphological, physiological, and biochemical responses when plants were exposed to the same water regime. In addition, we observed pronounced interactive effects of water regime and plant species identity on plant height, root length, root/shoot ratio, biomass, and contents of chlorophyll a, chlorophyll b, chlorophyll (a+b), carotenoids, malondialdehyde, soluble sugar, betaine, soluble protein and proline, implying that plants respond to water regime differently. Our findings may cast new light on the ecological restoration of grasslands and wetlands in the Qinghai-Tibetan Plateau by helping to select stress-tolerant plant species

Effect of Chitosan Coating with Different Molecular Weights on the Storage Quality of Postharvest Passion Fruit (Passiflora edulis Sims)

To study the preservation effect of chitosan coating with different molecular weights on postharvest passion fruit, the "Qinmi No.9" was coated with chitosan of molecular weights of 30, 50, 100, 150 and 200 kDa (1.5%, w/v) to determine the quality of passion fruit during storage. The results showed that chitosan coating with different molecular weights was able to delay the shrinkage and yellowing, reduce the weight loss rate and inhibit the decay of passion fruit. Moreover, chitosan with a larger molecular weight was more conducive to delaying the ripening and senescence of passion fruit, as well as reducing shrinkage, and decay. At the end of storage, the weight loss of fruits coated with 200 kDa chitosan was nearly 10% less than that coated with 30 kDa chitosan, and the fruits coated with 150 and 200 kDa chitosan did not decay. The lower molecular weight (30 and 50 kDa) and higher molecular weight (150 kDa) chitosan were more effective in inhibiting weight loss, total soluble solids and soluble sugar metabolism, and maintaining titratable acid, flavonoid and total phenol contents of fruit during storage. The chitosan with 150 kDa had the best effect in maintaining the vitamin C content, which was 1.12 times higher than the control group at the end of storage. In conclusion, chitosan with different molecular weights was effective to delay senescence, slow down water loss and shrink of passion fruit and maintain the quality, chitosan with 150 kDa was more suitable to maintain the quality of postharvest passion fruit