CFD Analysis of Tile-Repair Augers for the Shuttle Orbiter Re-Entry Aeroheating

A three-dimensional aerothermodynamic model of the shuttle orbiter's tile overlay repair (TOR) sub-assembly is presented. This sub-assembly, which is an overlay that covers the damaged tiles, is modeled as a protuberance with a constant thickness. The washers and augers that serve as the overlay fasteners are modeled as cylindrical protuberances with constant thicknesses. Entry aerothermodynamic cases are studied to provide necessary inputs for future thermal analyses and to support the space-shuttle return-to-flight effort. The NASA Langley Aerothermodynamic Upwind Relaxation Algorithm (LAURA) is used to calculate heat transfer rate on the surfaces of the tile overlay repair and augers. Gas flow is modeled as non-equilibrium, five species air in thermal equilibrium. Heat transfer rate and surface temperatures are analyzed and studied for a shuttle orbiter trajectory point at Mach 17.85. Computational results show that the average heat transfer rate normalized with respect to its value at body point 1800 is about BF=1.9 for the auger head. It is also shown that the average BF for the auger and washer heads is about BF=2.0

Rhythmic Pulsing: Linking Ongoing Brain Activity with Evoked Responses

The conventional assumption in human cognitive electrophysiology using EEG and MEG is that the presentation of a particular event such as visual or auditory stimuli evokes a “turning on” of additional brain activity that adds to the ongoing background activity. Averaging multiple event-locked trials is thought to result in the cancellation of the seemingly random phased ongoing activity while leaving the evoked response. However, recent work strongly challenges this conventional view and demonstrates that the ongoing activity is not averaged out due to specific non-sinusoidal properties. As a consquence, systematic modulations in ongoing activity can produce slow cortical evoked responses reflecting cognitive processing. In this review we introduce the concept of “rhythmic pulsing” to account for this specific non-sinusoidal property. We will explain how rhythmic pulsing can create slow evoked responses from a physiological perspective. We will also discuss how the notion of rhythmic pulsing provides a unifying framework linking ongoing oscillations, evoked responses and the brain's capacity to process incoming information

Shaping Functional Architecture by Oscillatory Alpha Activity: Gating by Inhibition

In order to understand the working brain as a network, it is essential to identify the mechanisms by which information is gated between regions. We here propose that information is gated by inhibiting task-irrelevant regions, thus routing information to task-relevant regions. The functional inhibition is reflected in oscillatory activity in the alpha band (8–13 Hz). From a physiological perspective the alpha activity provides pulsed inhibition reducing the processing capabilities of a given area. Active processing in the engaged areas is reflected by neuronal synchronization in the gamma band (30–100 Hz) accompanied by an alpha band decrease. According to this framework the brain could be studied as a network by investigating cross-frequency interactions between gamma and alpha activity. Specifically the framework predicts that optimal task performance will correlate with alpha activity in task-irrelevant areas. In this review we will discuss the empirical support for this framework. Given that alpha activity is by far the strongest signal recorded by EEG and MEG, we propose that a major part of the electrophysiological activity detected from the working brain reflects gating by inhibition

Exploring Hypersonic, Unstructured-Grid Issues through Structured Grids

Pure-tetrahedral unstructured grids have been shown to produce asymmetric heat transfer rates for symmetric problems. Meanwhile, two-dimensional structured grids produce symmetric solutions and as documented here, introducing a spanwise degree of freedom to these structured grids also yields symmetric solutions. The effects of grid skewness and other perturbations of structured-grids are investigated to uncover possible mechanisms behind the unstructured-grid solution asymmetries. By using controlled experiments around a known, good solution, the effects of particular grid pathologies are uncovered. These structured-grid experiments reveal that similar solution degradation occurs as for unstructured grids, especially for heat transfer rates. Non-smooth grids within the boundary layer is also shown to produce large local errors in heat flux but do not affect surface pressures

Trial-by-Trial Dynamics: A Window in Time

Contains fulltext : 87629.pdf (publisher's version ) (Open Access

Re-Entry Aeroheating Analysis of Tile-Repair Augers for the Shuttle Orbiter

Computational re-entry aerothermodynamic analysis of the Space Shuttle Orbiter s tile overlay repair (TOR) sub-assembly is presented. Entry aeroheating analyses are conducted to characterize the aerothermodynamic environment of the TOR and to provide necessary inputs for future TOR thermal and structural analyses. The TOR sub-assembly consists of a thin plate and several augers and spacers that serve as the TOR fasteners. For the computational analysis, the Langley Aerothermodynamic Upwind Relaxation Algorithm (LAURA) is used. A 5-species non-equilibrium chemistry model with a finite rate catalytic recombination model and a radiation equilibrium wall condition are used. It is assumed that wall properties are the same as reaction cured glass (RCG) properties with a surface emissivity of epsilon = 0.89. Surface heat transfer rates for the TOR and tile repair augers (TRA) are computed at a STS-107 trajectory point corresponding to Mach 18 free stream conditions. Computational results show that the average heating bump factor (BF), which is a ratio of local heat transfer rate to a design reference point located at the damage site, for the auger head alone is about 1.9. It is also shown that the average BF for the combined auger and washer heads is about 2.0

Static and Dynamic Analysis of Cracked Concrete Beams Using Experimental Study and Finite Element Analysis

In this paper, a simple method for defining the effects of cracks on elastic behavior of beam is presented. The cracked sections were modelled as rotational springs and the problem was solved using the finite element method. The global stiffness matrix of a beam with multiply cracked section was then assembled. For calculation of rotational spring stiffness equivalent to uncracked and cracked sections, finite element models and experimental test were used.The natural frequencies and mode shape of beams with multiple single-edge cracks were obtained and a new simple formula was proposed. Published numerical examples for cracked beams were used for validation

The necessity for monitoring insurance companies and the reasons for developing Iranian accounting standard No. 28

Nowadays, it is essential for Iranian insurance companies to provide monthly online reports on the performance, including the issued insurance policies and paid losses to the Central Insurance. The purpose of sending reports is to ensure compliance with the approved rates from insurance companies as well as other relevant regulations (see tariff control). All insurance companies are required to use the approved rates issuing the insurance contracts based on tariff control. In these circumstances there will be no possibility of competition between insurance companies. To attract more customers, adjustment of rates to change the contents of the contract is not possible. On the other hand, as the increase in market size happens, the insurance regulatory body oversees tariff uses and it is not able to monitor individually the rates of the insurance companies. Therefore, it is forced to limit their monitoring to the insurance rates which are high. Therefore, the secret violations and errors of insurance companies grow. To address the above problem, the Audit Organization of Iran with the help of Central Insurance issued accounting standard No. 28in 2006. The standard financial control has been replaced by a tariff control. This paper attempts to review the literature related to the current control of the insurance industry. The Iranian Accounting Standard No. 28 will also be extensively analysed

The necessity for monitoring insurance companies and the reasons for developing Iranian accounting standard No. 28

Nowadays, it is essential for Iranian insurance companies to provide monthly online reports on the performance, including the issued insurance policies and paid losses to the Central Insurance. The purpose of sending reports is to ensure compliance with the approved rates from insurance companies as well as other relevant regulations (see tariff control). All insurance companies are required to use the approved rates issuing the insurance contracts based on tariff control. In these circumstances there will be no possibility of competition between insurance companies. To attract more customers, adjustment of rates to change the contents of the contract is not possible. On the other hand, as the increase in market size happens, the insurance regulatory body oversees tariff uses and it is not able to monitor individually the rates of the insurance companies. Therefore, it is forced to limit their monitoring to the insurance rates which are high. Therefore, the secret violations and errors of insurance companies grow. To address the above problem, the Audit Organization of Iran with the help of Central Insurance issued accounting standard No. 28in 2006. The standard financial control has been replaced by a tariff control. This paper attempts to review the literature related to the current control of the insurance industry. The Iranian Accounting Standard No. 28 will also be extensively analysed