CFD Analysis of Nozzle Flow with Sudden Expansion In Aerospace Engineering

As the need for missiles and rockets has increased exponentially, the challenges associated with the gas dynamics of these vehicles continues to be a concern. The pressure in the downstream is sub atmospheric whenever there is a sudden expansion. This low pressure in the recirculation zone causes significant drag, accounting for almost two-thirds of the net drag of the aerospace vehicles. Hence, the purpose of this paper is to deliver a Computational Fluid Dynamic (CFD) analysis of the impact geometry and flow parameters have on the thrust force generated by the flow from convergent divergent nozzles to a suddenly expanded circular duct with a wider cross-sectional area. By observing all of the results, it is possible to conclude that the flow field in an enlarged duct is greatly influenced by the area ratio

Marginalized Importance Sampling for Off-Environment Policy Evaluation

Reinforcement Learning (RL) methods are typically sample-inefficient, making it challenging to train and deploy RL-policies in real world robots. Even a robust policy trained in simulation, requires a real-world deployment to assess their performance. This paper proposes a new approach to evaluate the real-world performance of agent policies without deploying them in the real world. The proposed approach incorporates a simulator along with real-world offline data to evaluate the performance of any policy using the framework of Marginalized Importance Sampling (MIS). Existing MIS methods face two challenges: (1) large density ratios that deviate from a reasonable range and (2) indirect supervision, where the ratio needs to be inferred indirectly, thus exacerbating estimation error. Our approach addresses these challenges by introducing the target policy's occupancy in the simulator as an intermediate variable and learning the density ratio as the product of two terms that can be learned separately. The first term is learned with direct supervision and the second term has a small magnitude, thus making it easier to run. We analyze the sample complexity as well as error propagation of our two step-procedure. Furthermore, we empirically evaluate our approach on Sim2Sim environments such as Cartpole, Reacher and Half-Cheetah. Our results show that our method generalizes well across a variety of Sim2Sim gap, target policies and offline data collection policies. We also demonstrate the performance of our algorithm on a Sim2Real task of validating the performance of a 7 DOF robotic arm using offline data along with a gazebo based arm simulator

Earthquake Induced Liquefaction Using Shake Table Test

Loose saturated cohesionless soils may undergo liquefaction due to strong ground motions. Such liquefaction causes significant damage to the structure resting on such soil. The extent of damage primarily depends upon soil properties, intensity of earthquake and type of structure. Various analytical models have been developed to estimate the likelihood of liquefaction of particular site based on field performance. However, if it is possible to identify the sites which are likely to liquefy due to specific intensity of earthquake it will help implementing the reduction in the damage which it would otherwise cause. One such analytical model has been developed by one of the authors of this paper and has been found to satisfactorily demarcate ‘Yes’ and ‘No’ zones of liquefaction for number of earthquakes. However, earlier research shows that laboratory tests could also be conducted to study the liquefaction behavior of soil under specific condition. The present study mainly deals with an attempt made in conducting Shake Table Test in laboratory by simulating earthquake conditions on site. The results obtained from the trial tests have been compared with the actual field cases and also with laboratory tests conducted for such soil by other researchers. It is observed that the criterion of the occurrence of liquefaction in the laboratory model is in close agreement with actual field data. Shake table test is found to be more effective in simulating the strong ground motion during earthquake

Unique Approach to Manage Patient Medical Records using Firebase

The world is in need for a system where every individual?s medical records ought to be handy or accessible. Although our generation is at the forefront of technological advancements more than ever, we still rely on paper based documents for accessing our medical records. While this is time-consuming, it is also an inefficient way of saving our records for use in the near future where we rely more and more on data stored electronically, helping us access it from any part of the world. Our aim is to build an application system which stores all details like allergies, medical history, surgery history, prescription drugs. We basically, keep a track of the person?s profile concerning his/her body?s biological trend. The app will be able to authenticate the user by using biometric sensors (if available on the phone) along with the national id number (Aadhar card number). Consider a senario where a patient is admitted to a nearby hospital, with the help of proposed system all his/her records could be seen without requiring them to speak for themselves. This could be of great help in case of blood transfusions or any other protocols followed in an emergency

Two Dimensional CFD Analysis on Different Rocket Nozzles

The reduction of Earth-to-orbit launch costs in conjunction with an increase in launcher reliability and operational Efficiency is the key demands on future space transportation systems, like single-stage-to-orbit vehicles (SSTO). The realization of these vehicles strongly depends on the performance of the engines, which should deliver high performance with low system complexity. Performance data for rocket engines are practically always lower than the theoretically attainable values because of imperfections in the mixing, combustion, and expansion of the propellants. The main part of the project addresses different nozzle concepts with improvements in performance as compared to conventional nozzles achieved by Different Mach numbers, thus, by minimizing losses caused by over- or under expansion. The design of different nozzle shapes and flow simulation is done in gambit and fluent software’s respectively for various parameter

Norfloxacin sesquihydrate

In the crystal structure of the title compound [systematic name: 1-ethyl-6-fluoro-4-oxo-7-(piperazin-4-ium-1-yl)-1,4-dihydro­quinoline-3-carboxyl­ate sesquihydrate], C16H18FN3O3·1.42H2O, N—H⋯O and O—H⋯O hydrogen bonds assemble the mol­ecules in a two-dimensional layered corrugated sheet structure parallel to the b axis. The water mol­ecules are disordered [occupancies 0.741 (11) and 0.259 (11)]

Transmission electron microscopic confirmation of the morphological predictions of the two-site model for hydroxyapatite dissolution

Hydroxyapatite (HAP) crystals were dissolved under two types of solution conditions designed to produce contrasting dissolution morphologies according to the recently proposed two-site model for HAP dissolution [Fox, J. L., Higuchi, W. I., Fawzi, M. B., and Wu, M. S., J. Colloid Interface Sci., 67, 312 (1978)]. In accordance with this model, dissolution into partially saturated buffers proceeded via formation of holes in the crystals, while dissolution of comparable amounts of material into completely unsaturated buffers showed no such holes. These results show that the two dissolution sites inferred from dissolution kinetics experiments are, in fact, physically distinct sites and that dissolution from site No. 1 results in hole formation. The physical location of site No. 2 is not yet certain.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22739/1/0000294.pd

Dissolution rate of apatite powders in acidic fluoride solutions and the relationship to hydroxyapatite disk and bovine enamel behavior

The dissolution kinetics of synthetic hydroxyapatite (HAP) and carbonate-containing HAP powders have been studied in fluoride-containing acetate buffer solutions partially saturated with respect to HAP (KFAP = 10-115 to 10-123). The experimental results indicate that in the case of HAP powders the dissolution rates become very slow when the KFAP values of the dissolution medium are larger than 10-119. For the carbonate-containing apatites, however, there is a significant dissolution in the region 10-115 >= KFAP >= 10-119 which is in the region of physiological and therapeutic significance.The present results with the HAP powder together with HAP pellet data show that the dissolution of HAP pellets in the region 10-114 > KFAP > 10-119 results from an extended transient period rising from sustained deposition of F- on the surface and at intermediate depths in the `lesion'. Similar effects have also been observed with bovine teeth dissolution in acidic F- solutions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25136/1/0000569.pd