Advanced space transportation technologies

A wide range of propulsion technologies for space transportation are discussed in the literature. It is clear from the literature review that a single propulsion technology cannot satisfy the many mission needs in space. Many of the technologies tested, proposed, or in experimental stages relate to: chemical and nuclear fuel; radiative and corpuscular external energy source; tethers; cannons; and electromagnetic acceleration. The scope and limitation of these technologies is well tabulated in the literature. Prior experience has shown that an extensive amount of fuel needs to be carried along for the return mission. This requirement puts additional constraints on the lift off rocket technology and limits the payload capacity. Consider the possibility of refueling in space. If the return fuel supply is guaranteed, it will not only be possible to lift off more payload but also to provide security and safety of the mission. Exploration to deep space where solar sails and thermal effects fade would also be possible. Refueling would also facilitate travel on the planet of exploration. This aspect of space transportation prompts the present investigation. The particle emissions from the Sun's corona will be collected under three different conditions: in space closer to the Sun, in the Van Allen Belts; and on the Moon. It is proposed to convert the particle state into gaseous, liquid, or solid state and store it for refueling space vehicles. These facilities may be called space pump stations and the fuel collected as space fuel. Preliminary estimates of fuel collection at all three sites will be made. Future work will continue towards advancing the art of collection rate and design schemes for pumping stations

An experimental study of near wall flow parameters in the blade end-wall corner region

The near wall flow parameters in the blade end-wall corner region is investigated. The blade end-wall corner region was simulated by mounting an airfoil section (NACA 65-015 base profile) symmetric blades on both sides of the flat plate with semi-circular leading edge. The initial 7 cm from the leading edge of the flat plate was roughened by gluing No. 4 floor sanding paper to artificially increase the boundary layer thickness on the flat plate. The initial flow conditions of the boundary layer upstream of the corner region are expected to dictate the behavior of flow inside the corner region. Therefore, an experimental investigation was extended to study the combined effect of initial roughness and increased level of free stream turbulence on the development of a 2-D turbulent boundary layer in the absence of the blade. The measurement techniques employed in the present investigation included, the conventional pitot and pitot-static probes, wall taps, the Preston tube, piezoresistive transducer and the normal sensor hot-wire probe. The pitot and pitot-static probes were used to obtain mean velocity profile measurements within the boundary layer. The measurements of mean surface static pressure were obtained with the surface static tube and the conventional wall tap method. The wall shear vector measurements were made with a specially constructed Preston tube. The flush mounted piezoresistive type pressure transducer were employed to measure the wall pressure fluctuation field. The velocity fluctuation measurements, used in obtaining the wall pressure-velocity correlation data, were made with normal single sensor hot-wire probe. At different streamwise stations, in the blade end-wall corner region, the mean values of surface static pressure varied more on the end-wall surface in the corner region were mainly caused by the changes in the curvature of the streamlines. The magnitude of the wall shear stress in the blade end-wall corner region increased significantly in the close vicinity of the corner line. The maximum value of the wall shear stress and its location from the corner line, on both the surfaces forming the corner region, were observed to change along the corner. These observed changes in the maximum values of the wall shear stress and its location from the corner line could be associated with the stretching and attenuation of the horseshoe vortex. The wall shear stress vectors in the blade end-wall corner region were observed to be more skewed on the end-wall surface as compared to that on the blade surface. The differences in the wall shear stress directions obtained with the Preston tube and flow visualization method were within the range in which the Preston tube was found to be insensitive to the yaw angle

Living by the Sword: The Free Exercise of Religion and the Sikh Struggle for the Right to Carry a Kirpan

Sikhism is a 500 year old religion with a growing presence in the United States. However, one of the articles of faith required for Sikhs, a kirpan (a ceremonial sword), conflicts with the norms of American life for these often misunderstood people. This paper gives a brief primer on Sikhism and discusses some of the day-to-day problems and recent issues facing kirpan-carrying Sikhs in North America. Upon reviewing the current state of free exercise jurisprudence as applied to the kirpan, I outline several suggestions for the acceptance and accommodation of kirpans

Prevalence of retinopathy of prematurity: a 3-year retrospective study

Background: Retinopathy of prematurity (ROP) is a vasoproliferative disease of premature infants which leads to permanent blindness. Early screening is needed to diagnose ROP and prevent blindness.Methods: Retrospective study was conducted in 225 neonates from January 2018 to December 2020. All neonates with birth weight 0.05). Out of 148 neonates who were given oxygen 19 (12.83%) developed ROP (odds ratio: 5.52). Out of 42 neonates who had sepsis, 2 (4.76%) developed ROP (odds ratio: 0.43).Conclusions: The prevalence of ROP was 9.33%. The prevalence is showing a decreasing trend. ROP is not affected by gender. Oxygen given to neonates is associated with greater ROP. But sepsis in neonates is not associated with development of ROP

Political network structures as a special form of management

В статье исследуются основные подходы к анализу политических сетевых структур и возможность использования сетевых структур в современном управлении.This article examines the main approaches to the analysis of political networking and the use of network structures in modern management

Hydrochemical Characterization, Classification and Evaluation of Groundwater Regime in Sirsa Watershed, Nalagarh Valley, Himachal Pradesh, India.

Nalagarh valley is the southernmost expanse of Himachal Pradesh; belong to the rapid industrial belt of Baddi, Barotiwala and Nalagarh (BBN). The present investigation is to examine the suitability of groundwater quality for drinking purpose and factor prevailing hydrochemistry by collecting 32 groundwater samples during pre and post monsoon. The physical and chemical analyses result shows the parameters like Cl-, HCO3-, SO42-, NO32- are well within desirable limit as per BIS. At some locations the concentration of pH, TH and Mg2+ exceeded the permissible limits and nearly 50% samples of EC, TDS, Ca2+ shows above the desirable limit of BIS which gives us cautions. Classification of hydrochemical facies of groundwater revealed that all the samples belong to the Ca2+-Mg2+-HCO3- water types. Based on the Soltan’s Classification, the groundwater sample are categorized normal chloride, normal sulfate and normal bicarbonate water type. Base-exchange indices and meteoric genesis indices indicates majority of samples belongs to Na+- HCO3- and shallow water percolating type are 93.75% and 90.63% respectively. According to Gibb’s ratio, the entire water sample fall in the rock dominance field for both season. Key words: Water resources, Groundwater Quality, Hydrochemical facies, Base-exchange indices, Gibb’s rati