Mechanical and Structural Behavior of Granular Material Packed Beds for Space Life Support System Applications

Long-term human mission to space, such as living in International Space Station (ISS), Lunar, and Martian bases, and travel to Mars, must m ake use of Advanced Life Support Systems (ALSS) to generate and recycle critical life supporting elements like oxygen and water. Oxygen Gen eration Assembly (OGA) and Water Processor Assembly (WPA), critical c omponents of ALSS, make use of series of granular material packed beds for generation and recycling of oxygen and water. Several granular m aterials can be used for generation, recycling, processing and recovery of oxygen and water. For example, they may include soft bed media, e.g. ion exchange resins for oxygen generation assembly and hard bed media such as, activated alumina, magchem (Magnesium oxide) and activa ted carbon to remove organic species like ethanol, methanol, and urea from wastewater in Water recovery/processing assembly. These beds are generally packed using a plate-spring mechanism to provide sufficien t compaction to the bed media throughout the course of operation. This paper presents results from an experimental study of a full-scale, 3 8.1 cm (15 inches) long and 3.7 cm (1.44 inches) diameter. activated alumina bed enclosed in a cylinder determining its force-displacement behavior, friction mobilizing force, and axial normal stress distribu tion under various axially applied loads and at different levels of packing. It is observed that force-displacement behavior is non-linear for low compaction level and becomes linear with increase in compaction of the bed media. Axial normal stress distribution along the length of the bed media decreased non-linearly with increase in depth from the loading end of the granular media. This paper also presents experimental results on the amount of particulates generated corresponding to various compaction levels. Particulates generated from each of the tests were measured using standard US sieves. It was found that the p articulates and the overall displacement of the bed media increased with decrease in initial compaction of the bed media. This effect could be attributed to the greater tendency for inter-particle sliding/rub bing due to smaller internal friction angles, as seen from the shear tests, at lesser initial compacted levels. Upon unloading, it was obse rved that there was no change in displacement (especially rebounding) in the bed media. This effect could be attributed to the fact that th e porous activated alumina particles fracture/break upon increase in applied load (during loading phase) and occupy void spaces in between the material grains; thereby leading to settling of the media. The lo ad-displacement curve becomes more linear with increase in initial compaction of the bed media. It is concluded that compaction considerabl y affects the load-displacement behavior of the bed media. A series of tests were also conducted on the packed bed media to determine the f orce required to mobilize the friction between the bed media and the housing cylinder. The results from these tests showed the existence of significant friction between the bed media and the encasing stainles s steel cylinder. Further, it was found that friction effects were more pronounced for media with higher initial compaction. Internal frict ion of the granular media was measured using direct shear apparatus. It was observed that the internal friction increased with increase in initial compaction of the bed media. In this study, a computational m odel (CM) is also developed using finite element software ANSYS to verify experimental results obtained for the distribution of the axial n ormal stress and axial displacement along the length of the full-scal e activated alumina bed media. In the computational model, the granular material is considered to have appropriate failure and frictional c ontact exists between the wall and the granular media. It is observed that the model predicts results closely with the experimental method. The compational results show that the axial normal stress distribution along the length of the activated alumina media decreases non-linea rly from the loading end and is negligible beyond a certain depth. Th is can be attributed to the existence of friction between the walls and the media and that the friction takes up most of the applied load

Evolution of foetal echocardiography as a screening tool for prenatal diagnosis of congenital heart disease

Congenital cardiac anomalies are the most common anomalies, with an estimated incidence of about 4-13 per 1000 live births. Proper perinatal and neonatal management is dependent upon accurate prenatal diagnosis. Approximately 10% of foetuses with cardiac abnormalities have identified risk factors; hence, most of the anomalies occur in pregnancies without prenatal risk factors. Foetal echocardiography allows for prenatal diagnosis of congenital heart disease and serves as a routine screening tool for congenital heart defects. Advanced technology, has not only allowed more accurate and early detection of cardiac abnormalities but has also improved the care and outcome of selected foetuses with severe cardiac malformations or arrhythmias. It can also identify patients for in-utero cardiac interventions. Prenatal diagnosis of congenital heart disease has allowed for better counseling and preparation of families regarding the expected prenatal development of the foetus as well as the anticipated postnatal management strategy and prognosis

Effect of harmones on callus induction in Maize (Zea mays L.)

Callus induction from explants is a critical process in regeneration, micropropagation and transformation of maize (Zea mays L.) plants. Formation of callus from plant tissues on culture is affected by several factors. This study revealed to establish the effect of genotype, source of explants and auxin concentration on callus induction from five genotypes UMI 757 (G1), UMI 615 (G2), UMI 112 (G3), UMI 285 (G4) and CO 1 (G5) and one hybrid CO H (M) 5 (G6). Callus induction of the six maize varieties was investigated using immature embryos (E1), leaf bits (E2), root tips (E3), hypocotyls (E4) and seeds (E5) as explants with different concentrations of hormones. In this study, immature embryo was taken from 10 to 12 days after pollination (DAP) to get maximum response. The highest percentage of callus induction was observed (99.10) in immature embryo culture and seed culture gave the highest percentage of rhizogenic callus formation when compare to immature embryo. Among the genotypes tested, CO H (M) 5 recorded the highest callus induction percentage on (2D2K2) medium composition

Preliminary phytochemical studies for the quantification of secondary metabolites of medicinal importance in the plant, Acalypha fruticosa Forssk

The medicinal plant, Acalypha fruticosa Forssk for the treatment of dyspepsia, stomachache, fever, jaundice, skin diseases and even as an antidote is generally distributed in different environments of tropical region in Coimbatore district of Tamil Nadu. However, its occurrence is more common in lower hills of Western Ghats and other habitats in this region where the soil is stony with low moisture. So far, there was no study on the influence of habitat conditions on the change in the content of secondary metabolites of medicinal importance in this plant. Hence to know the changes in the content of such secondary metabolites in the leaves of A. fruticosa, the present study was undertaken in three different habitats. Thin layer chromatography revealed the presence of phytochemical compounds viz., alkaloids, flavonoids and saponins in the leaves of all the three populations. Further the content of all these compounds are found to be higher in the population of dry habitats

Need to Know the Tribes of Tamil Nadu

Tribes are those who have seen the evolving changes from the ancient ways of life and have regulated their lives. Their social organization culture and culture is found according to the context in which they live. The so-called tribes are variously called in Tamil. Politicians refer to them as savages, literati, hill people, rain people, Tolkudi, Mudukudi, Adigudi, Purvagudi, and Gandhians refer to Gandhi as Kirijan. The tribe is an educated social group. These are people who can consistently live in a common place. Speakers of the common dialect are those who have a common one-sided social morality. Followers of common ancestral beliefs panchayat systems and religious belief systems. The Fifth Principle of Sangam Literature shows that it was the hill people who formed the way of life and culture of the ancient Tamil community according to their landscape. Thus, the majority of the indigenous people are indigenous peoples with traditional cultural identities

A Variable-Structure Variable-Order Simulation Paradigm for Power Electronic Circuits

Solid-state power converters are used in a rapidly growing number of applications including variable-speed motor drives for hybrid electric vehicles and industrial applications, battery energy storage systems, and for interfacing renewable energy sources and controlling power flow in electric power systems. The desire for higher power densities and improved efficiencies necessitates the accurate prediction of switching transients and losses that, historically, have been categorized as conduction and switching losses. In the vast majority of analyses, the power semiconductors (diodes, transistors) are represented using simplified or empirical models. Conduction losses are calculated as the product of circuit-dependent currents and on-state voltage drops. Switching losses are estimated using approximate voltage-current waveforms with empirically derived turn-on and turn-off times

Study on Key Determinants for TQM Adoption in Construction Practices: An Indian Perspective

The purpose of this paper is to explore the factors that influence the implementation of TQM practices in the construction industry. The study was conducted in Tamil Nadu from June 2015 to January 2016. The researchers used a random sample approach to collect data from participants. A questionnaire-based approach was chosen to collect information from participants. Statistical tools such as Cronbach's Alpha, exploratory factor analysis, multiple regression, correlation, standard deviation, and coefficient variation were employed in the study. Nine crucial dimensions of TQM implementation were identified: customer-oriented factors, organizational culture factors, internal communication factors, supplier-related factors, employee participation factors, employee development factors, employee training factors, availability of equipment factors, and process improvement factors. TQM implementation is influenced by a number of factors, including but not limited to customer-oriented factors; organizational culture factors; employee participation factors; employee development factors; availability of equipment factors; and process improvement factors. The study found that TQM implementation is driven by customer-oriented factors. Among engineers and project managers, the focus on customer-oriented factors was the highest. The results of this study can be used to inform policy makers, helping them create effective TQM policies in the construction industry